Pioneer RT-707 service & rebuild

[GPS16]

Hi,

nice pickys about the reverse button. Glad you got hold of one. That would have annoyed the hell out of me too!!!

When I said Reverse, that is what I meant. Again, you do not indiscriminately FF/Rew with a test tape!!!! I can't think of a good way to "Soft Rewind" with a 707. With a Revox A700 you can enforce one with the tape tensioners as the motors are under servo control at all times. The C270 has a DIP switch internally to select "Library "Wind" but I must admit I have not tried that yet!!!!.

You are going to end up with a fine machine when you are done!!! Later on when a recording done on the machine by you gets you grinning, like me you will think that the test tape was worth every penny (or should I say Cent)!!! A quality recorder CANNOT give you it's best without the use of one!!!!!!! Recorders of this class need to be treated with the respect they deserve. As I have said before, hearing the quality these recorders can convey is one thing. Knowing what is going on under the bonnet (hood) adds that extra dimension.

I am the family bore on these things, my brother is the cars and engines one!!!

GPS16

 

[smurfer77]

I'm drawing up my parts list for the rebuild (the recalibration is being delayed until I at least replace the VRs, which are pieces of fiddly junk). Regarding the transistors, are any particular devices used in this machine known to be noisy? I'm use to working on gear a decade or two older than this and not familiar with the particular devices used here. Finding substitutes is not a problem but I may not replace the transistors if they are known to be low-noise and reliable. My ears tell me that I don't have especially noisy transistors in the machine and when listening via headphones the hiss noisefloor is very low.

I'm especially interested in hearing comments on audio quality of the IC used in the head amp (note: "head" amp is the front end amp that all signals go through, not the headphone amp (the headphone amp is just an extra stage on the back of the playback board after line level amplification). It wouldn't be that hard to replace the package with (carefully matched) discrete components. The TA7129P IC is a 7pin preamp package which houses 3 transistors (see image below) but to me everything sounds find so I'm reluctant to go crazy with hardcore substitutes. The schematic below is actually taken from the TA7129AP (specs available on image 1 of that page), but this could be pretty much the same at the TA7129P since the NTE1462 (a known TA7129P equivalent) has the same (identical) specs at the TA7129AP. If anyone has the datasheet for the TA7129P please share it. For now I'm just assuming that the "A" suffice means a slightly higher gain or voltage capability, which is what it usually means.

 

[GPS16]

Hi,
as far as I am aware, there are no issues with noisy transistors. These seem to be associated with Akai machines. As you have said, your ears are telling you that you have a low noise floor so I would leave it alone. If it ain't broke, don't fix it, as they say. I would hate the only result of my efforts being reduced reliability due to lifting print on PCBs from repeated soldering.

The "A" suffix on the amp chip may be a lower noise variant. In an A700 there are 3 variants of the TBA931. The "3" version used in the head amp was the one with the lowest noise bandwidth spec.

Replace the pots, aligned the beast and then take things from there.

GPS16

 

[smurfer77]

[EDIT: parts list in service manual for head amp is per each pcb board. There are 2 head amp boards. Updated cap list images to include both head amp boards.]

Okay I am leaving the transistors alone until they give me trouble or I learn about unreliable parts. I've made a list of substitutes for the transistors though and if anyone should want the info, let me know.

I've also decided to leave the non-electrolytic capacitors alone. I sometimes replace ALL capacitors when doing rebuilds, but I like so much how this unit sounds I will replace only the electrolytic caps (and honestly, doing all caps is a lot of work), which may reach the end of their lifetime sooner than the other cap types (some of which arguably should last forever if not abused). I've made a spreadsheet of all parts in the machine, but maybe I will post those piecemeal, board by board, as I rebuild. For now, here is the complete list of electrolytics:

and the short version if you upgrade some of the voltages.

I've put in my order on Mouser for the caps and Bourns multiturn VRs for the EQ/Gain/VU/record_lvl/record/bias.
- Note that some of the smaller value electrolytics (C ≤ 1 uF) are being replaced by WIMA polypropylene film caps. I looked into replacing electrolytics in the range of 2-10uF, but here the size of the film caps was going to make the substitutes untidy.
- many of the max voltages have been upgraded when I ordered, especially for the power filter caps, to improve lifetime. I kept all capacitances the same (although you could upgrade the power filter cap values if you wanted, you should (generally, although there are some other exceptions in the circuits) keep everything else the same).
- I took note of which caps are in the signal path, from heads to line and headphone output, and made sure to use my favourite caps there (WIMA film caps where possible, otherwise nichicon FG. I know it's not nichicon's TOTL but I prefer these based on experience over other nichicon. I like Elna historically but I find it very hard to take the silk hype seriously, it's just turns me off to read stuff like that in datasheets. (I've tried them and they do sound fine though. Might be tempted to use them where I didn't want to alter the look of a particularly rare device since the caps look more the vintage brown part, than the shiny nichicon gold).

Later when I do the rebuild I will report on bad caps I find, but I want to stress that I don't think this recap is completely necessary. My personal experience is that while there are some problematic brands/types of caps you need to be aware of, electrolytic caps sometimes get bad press on the forums, beyond what they deserve. I've replaced literally thousands of electrolytics and I've tested capacitance and leakage current of many at low and operating voltage and found very few problem caps (maybe less than 10 in my career) and I don't share the point of view that all old electrolytics must be replaced. YMMV and lets not turn this thread into an electrolytics conversion since it has been had elsewhere multiple times. Another issue is if you aren't skilled with a soldering iron you can put a lot of wear and tear on the PCBs and traces. So why am I replacing all of the electrolytics? Mainly because I just want to future proof the machine. That, and I'm obsessed with extracting the maximum possible performance from units without modifying their circuits when I can help it. Do I expect an audible improvement from the replacements? No. It will be subtle, if audible at all. But I will have piece of mind that the values are all good. Sometimes the old caps are higher quality and beefier than what you can buy now so you need to really use some judgement in what you replace IMO. Sometime you devalue devices by replacing parts, but I don't think this will be the case with the RT-707 (it's not rare at all). The final point is that I'm the type who would check values of every single cap and that often requires lifting a leg from the PC. It's only a bit more work to desolder the other leg and just replace the cap while you are there and be more confident that the electrolytics are good for a few more decades.

 

[GPS16]

Hi,

with machines of this age, I would still be looking to change the Electrolytics en mass. With low voltage gear, the caps were chosen for their working voltages to be a percentage above what will be seen. As a rule of thumb there will not be too much head room. Also there can generally be comparatively large ripple currents which have associated power dissipation within the caps, due to the ESR, which over time accelerates the drying out of the electrolyte. By comparison, in older valve gear, the operating voltage was chosen so that the caps could withstand the applied voltages under fault conditions. If faults included valve non conductivity, the voltages present across capacitors could lift to alarming levels as there are no volt drops across resistive droppers and filter resistors. These caps were hardly stressed during normal conditions and consequently could last for years and years. As you have mentioned, where ever possible, the capacitance remains the same, The voltage working was judged on the old capacitors physical dimensions. If the larger working voltage would fit........ Do not try to put larger capacitance reservoir caps in place. This could increase turn on surges to the point of popping semiconductors elsewhere!

I also look at the circuitry and assess the position of any Disc Ceramic caps. These can also degrade and go leaky due to ingress of moisture. Any in the signal path would also be replaced.

From experience with the A700s, Tantalum Beads are also at the end of life and need to be replaced. I had ticks and pops on my first A700 when any of the switches were change state. The Tants used as DC blockers were found to be leaky. They were also changed en mass.

I agree that WIMA replacements for small values is of benefit. It is not a great expense to do so. We are not concerned about profit margins at this stage of the game only improvements!!!

There is a capacitor in the Power Supply section which acts as a time constant (C408). Make sure that this one is replaced and with a quality component. If this one fails the solenoids may get cooked. The circuit involved hits the solenoids with a high voltage to pull in the solenoid and the drops the voltage over time to a much smaller holding current. As this cap gets leaky, the holding voltage increases and ramps up the long term dissipation in the solenoid coils. At 9.5 cm/s and 1800 ft of tape this is 1.5 hours duration on a regular basis. Well it was on my machine!!!!

That should keep you happy for a while!!!

GPS16

 

[smurfer77]

You have convinced me to go all out on the refurb. Revising the part list and will put in another order soon. All of the ceramic and mylar will be replaced. Think I will probably replace the styrol caps too although they are probably fine (these are polystyrene film caps right? Anyway, I will consider changing over to modern WIMA polypro film caps).

One thing I'm debating is the two metalized paper caps C921 and C922 (I think these are the two off board caps you can see (even in the service manual layout pic) mounted on chassis just below the servo board). I'd post a pic but I'm at the office now....

Thanks for the tip about C408. I'm replacing all of those with double voltage cap but will make sure this is a solid component. looks like that is a
22 uF 35 electrolytic. I'm replacing with a nichicon 50 V cap but may consider beefing that up further...

 

[GPS16]

Hi,
Personally I would be leaving the mylar caps where they are. From experience I have seen troubles with ceramics but not with mylars. The polystyrene and polypropylene caps would be left alone also. The 2 caps near to the servo PCB (C921/2) leave alone. They are motor run caps and should be conservatively rated in the first place. If you end up with speed stability problems following their replacement you could be "leading your self up the garden path" as they say, that is apart from servo PCB problems if the replacements fail. The servo PCB puts just enough power into the motor to achieve the correct speed. If the speed cannot be achieved due to faults elsewhere, the servo will pour power into the motor to try and achieve it. Fuses will be the only saviour under these conditions and by then it may be too late. As the motor drive is not sound, the problem will not be a "full speed" one. Sorry to sound alarmist but component replacement should be beneficial and not detrimental. Changing components to enhance sonic quality is one thing. Leave the others, which are not in the signal path, alone and treat the rest on their merits individually.

Whilst renovating the Revox machines I have, I did Electrolytics, Tantalums en masse and Ceramics in the signal path. All others are as was. If too much is replaced and then the machine will not set up. Where do you start!!!! Hopefully you will not have to resort to putting the old ones back in again!!!

Keep going. You are doing a great job. Just apply the brakes a bit!!

GPS16

 

[smurfer77]

okay, will replace just the electrolytic and ceramic caps for now. Most of the ceramic discs are getting replaced by WIMA polypro film caps, down to 33pF value, and below that I'm using those little blue murata C0G ceramics that I've had success with in amps (and the WIMA caps don't go down to those values). Thanks for the info about C921/2 - they do look pretty beefy upon inspection. I'm adding pics here to show which caps (I think) they are because it took me a while to figure out where they are and that they are not on the servo board (since they are listed in the servo board parts list).

And, here is the complete list of the non-electrolytics:

 

[smurfer77]

Still waiting for the new batch of parts to arrive still, but just had a thought. Using my 250 Ohm headphones (Beyer Dynamic DT-150 - love them) the headphone output is too loud. And, the headphone output is fixed which is kind of annoying honestly.

Looks like the headphone signal splits off near the end of line stage amplification (just after Q109/110) and then goes through transistor stage via Q111/112. The output from the Q111/112 drives the headphones and the level meters. So I'm thinking about knocking down the signal at the output with an new resistor (or maybe a VR). I guess another option is to modify the gain of Q111/112.

 

[GPS16]

Hi,

If you wish to reduce the phones output, put series resistors in the wiring to the phones socket. The voltages at the primary to the small transformer needs to be set where it is. This is the reference feed to the VU meters. It is the first setting done in the calibration procedure as the 1kHz reference level. Moving this voltage around is not a good idea!!!!

Cheers.

GPS16

 

[smurfer77]

Ah yes. of course. And I even noticed the vu meter is driven from there. Okay. will knock down the signal at the end of the line.

Cheers
David

 

[smurfer77]

I've now had a chance to start the recap. The control board (the one mounted on the left side - see pic below) was one of the first sections to get done.

To pull this board out I found it necessary to remove the black plastic box are the rear that houses the inputs and outputs:

Then after undoing the screws and wire harness (visible in later pics) you can slide this board up and out:

Note that to transistors mounted on the PCB are screwed to the metal mount for thermal management so make sure you unscrew everything before yanking at the PCB to remove it. I cleaned up the metal mount by rubbing it down with oil - this will inhibit oxidation a bit too.

Okay, here is the original board:

One minor annoyance is that the biggest axial capacitor was firmly glued to the PCB. So I snipped the leads from the top, and applied a little alcohol to soften the glue, then rocking it side-to-side (across it's width) it came loose. You can see the the old thermal paste has been cleaned off of the transistors.

Here you can see the board with electroytics replaced. No ceramics on this board and mylar were left alone. GPS mentioned in post #45 that c408 (22 uF, 35 V) is important so I beefed it up to a 22uF 400 V cap to hopefully improve lifetime (basically I went as big as i could given the clearance of the board to the metal), which you can see in this pic (the maroon cap). I might sleeve the axial caps if I pull that board out again.

Okay, so I screwed it back onto the mount, bending the transitor legs gently, so they sit off of the metal like this so I could more easily apply new thermal paste:

Then slotted it back into the chassis.

Here is a pic showing the clearance of the caps I used. For reference, there is 24 mm of clearance between PCB surface and metal.

Here is a list of parts I made for the control board for reference (i'm just doing any electrolytics and ceramics for now).

The temperature of the two mounted transistors at my present ambient temperature of about 73 F (23 C) is just over 30 C, which is a few degrees cooler than before so probably the thermal paste had lost is properties a bit over time.

I didn't mess up any pcb traces - not fragile compared to what I'm use to. I reflowed the lacquer with a bit of solvent just to clean things up a bit though - looks better than original now. Tested operation of the RT-707 for a while before moving onto another section (which I think is always good policy) and everything seems to be good. FYI all removed components tested okay.

Onward!

 

[smurfer77]

Moving to the EQ board, which is the little board mounted vertically on the power & oscillation board, I am leaving the transistors alone for now. Mylar caps are staying too; only electrolytics and ceramics are being replaced at this stage, unless something measures out-of-spec. The EQ board actually doesn't have any electrolytics, and that's probably a good thing given is sensitive purpose, so it's just the 8x ceramics to be replaced now.

Here you can see the original board.

Here you can see the 8x ceramic caps and their WIMA polypropylene film replacements.

And the board after substitution:

While all of the ceramics are all operational I did measure more variation of capacitance than I would like in the EQ amp. Values were spread between 7.4 nF and 9.5 nF (i.e. -26% to -5% compared to the nominal value in schematic of 10 nF (0.01 uF)). The replacement film caps were all within 5% of 10 nF (with most being within 1-2%).

It was mentally hard for me to not change the transistors while I had the board out on the table since I have a box full of suitable replacements (KSC1815, or 2nd preference ZTX694B). However, I'm used to working on much older gear where noise is often an issue with older transistors, but so far I'm not convinced this is an issue here, and this is a part of the circuit I want to mess with least since i don't want to mess EQ. Same goes for the mylar caps here - will replace only if i see a problem.

Again, tested board before moving to next section. All is well.

 

[smurfer77]

I actually did start on the power & oscillation board next since it is convenient while the EQ board is removed from it. However, to access the transistors mounted onto the vertical metal heat sink on the power & oscillation board it is convenient to remove the head amp boards (mounted vertically on the adjacent playback board). So onto the Head Amplifier Assembly (RWF-070) boards before the power & oscillation board. Again, I'm leaving alone the semiconductors unless I find a problem in measurement. The Polystyrene and mylar caps are remaining unless I find a problem too; I'm replacing just the electrolytic and ceramic caps, unless I find problems elsewhere.

The number of parts here is for BOTH head amp boards.

Might be worth stopping and discussing removing the vertically mounted boards since there are a few to remove (these two and the EQ board). You can get the boards out with a lot of patience if you don't have the right tools, by heating a few prongs at a time and wiggling the board out a bit at a time, going back and forth heating prongs and getting another millimetre at each end... but a better way is to use a decent solder sucker on all prongs, and after that some desoldering braid to get the last drops of solder - the boards just fall out. Basic stuff, but I remember going a long time without buying these tools/materials, even though they are cheap. (Note: not all solder suckers are equal. This doesn't mean you have to get an expensive one).

Here are the original boards. Like several of the boards in my RT-707, the lacquer on the PCBs is a bit messy, so I reflow the lacquer on each when I'm done soldering. Compare for example the messy right board here and look at final boards below

Here is the IC amp (TA7129P) that was discussed in discussed in posts #42 and 43 (there I debated replacing or rebuilding with discrete components but discarded the idea since nobody has complained about this part). I like how vintage and classy the polystyrene caps just left of the orange caps look.

Here are pics of the finished boards:

And finally, installed back in the playback board (after doing my work on the power & oscillation board transistors, which I will report later).

If you compare to the original boards you will notice two resistors have disappeared. This is because my C1105/6 (100 uF, 10 V) got a bit too large in the 50 V version I ordered. The resistors were displaced; they are mounted from the rear as seen here.

I measured all of the removed parts, except the 15 pF caps (which is getting close to the edge of my measurement range). All caps were okay, but again with large variation of value ~20% or 30% in some cases.

I've reinstalled and tested the boards before moving to the next section and luckily everything is again okay first go.

 

[GPS16]

Hi Smurfer,

nice job. I see that you mention ZTX694B transistors. I work for Zetex which is where the name comes from. The ZTX transistors were the mainstay when Ferranti/GEC Plessey Semiconductors ditched the discrete business. Zetex was then formed following a management buy out. They came up with the name from the ZTX of the product they were making. When I first entered the forum, we were still GEC Plessey Semi (GPS16). I hand been working there for 16 years at the time. Since that time we have been bought out again. We are now part of Diodes Inc.

The ceramic caps on the Eq PCB do not need to be close tolerance. They are for transient suppression on the bases of the switching transistors. The audio does not go through them only DC voltage for Eq selection.

The larger caps will need to be glued down or the whole machine would not pass the environmental/vibration test which are part of the QA testing. The caps will shake around and rip the wires from the PCB.

Keep up the good work.

GPS16

 

[smurfer77]

Hi Smurfer,

nice job. I see that you mention ZTX694B transistors. I work for Zetex which is where the name comes from. The ZTX transistors were the mainstay when Ferranti/GEC Plessey Semiconductors ditched the discrete business. Zetex was then formed following a management buy out. They came up with the name from the ZTX of the product they were making. When I first entered the forum, we were still GEC Plessey Semi (GPS16). I hand been working there for 16 years at the time. Since that time we have been bought out again. We are now part of Diodes Inc.

The ceramic caps on the Eq PCB do not need to be close tolerance. They are for transient suppression on the bases of the switching transistors. The audio does not go through them only DC voltage for Eq selection.

The larger caps will need to be glued down or the whole machine would not pass the environmental/vibration test which are part of the QA testing. The caps will shake around and rip the wires from the PCB.

Keep up the good work.

GPS16

The ZTX transistors are keeping my sansui amplifier collection going strong - used those 694B and 795A on most of the driver boards. It's funny. Some time ago I was thinking about these little transistors i buy, and hoping they keep some nice people in jobs somewhere across the globe!

About the ceramic caps on the EQ board, thanks, I now see they are all just hi-passing transients to ground, so no need to be too worried about value matching. cheers.

Okay, will glue the big caps down to keep everything secure - I will note in this thread which caps were factory glued as I go along. (note to self: use something non-corrosive, keeping in mind the death glue found in some amps I've worked on).

Cheers
David

 

[smurfer77]

Here is a shot of the almost original power & oscillation assembly board (with just two caps replaced and two pulled out, and of course EQ board is pulled out. You could do this work with it in, but it will be less pleasant). The four biggest caps (bottom right) are all glued to the PCB. There is no way to snip the legs on the top of the pcb so I sucked the solder and used the desoldering braid again. I tried at first just rocking the caps a bit but they are glued on well enough that I was fearing for the PCB. So again I applied a dab of alcohol and then tried again after a minute - they came off much more easily after softening up the glue.

Here you could see that not too much glue was applied (but it sure holds on well).

And after some cleaning up.

Here is the parts list for this board. Again, i'm just doing the electrolytic and ceramic caps unless I find problems with other parts.

Oh and here is why I pulled out the head amp boards on the playback assembly before doing this; to access these transistors easily.

I've pulled the heat sink out and cleaned off the paste from all surfaces. Like on the control board, I've pulled the transistors out from the heat sink to more easily reapply paste and insert the mica insulators.

And here we go, a bit messier than I would like, but better than before:

And a view of the finished board from the other side:

And for the heck of it, a close up of the EQ board fitted into the redone power board:

Again I checked all of the removed parts and they measured okay. One funny thing happened. When I was mearing i came across some 2.2 uF caps and I couldn't remember installing any 2.2 uF caps. Sure enough, I had installed 22 uF caps - the font on the original caps is tiny. Same goes for the font of the 4.7 uF caps although I didn't make the same mistake there. So I pulled the wrong caps out and but new caps in. Here is a pic of the little caps and you can understand how I made the mistake in my poorly lit work area.

In case you couldn't tell already, I'm a bit of a shutter bug. And guess what, I like taking infrared (IR) pics too.

Here is the 707 from the top-rear.

okay, so what? Well, I've found this a useful tool for finding places that are hotter than they should be by malfunction, fault part, or as result of the original design. In some cases I have remounted or changed components where I though the temps were too high for that part. I have a little IR thermometer too which is still handy, but the IR camera really stops me from missing things.

Okay, what does this have to do with the power & oscillation board. Well I just want to show a couple of things.
First, the transistors mounted onto the sink are 5 C cooler after new paste. You often here people claim such things, and it makes total sense, but a picture says a thousand words. Here is before new thermal paste:

And here is after new thermal paste (sorry for 90 degree rotation from before pics):

We can see that the transistor on the right is a bit warmer than the others due to proximity to something hot (the difference is not due to the transistor operation itself, just it's position). This one on the outer most part of the PCB is R334, 3.3 kOhm, 1/4 W. In the pic below you can see it hits well over 50 C. Not necessarily a problem, but I might bump that up to 1 W later - I have some nice xicon laying around for sure. If someone thinks the temp dependence of resistances was built into circuit design, let me know (I've seen it before).

Just next to that, on the other side of the heat sink is R332 3.3 kOhm, 1/4 W, which is hitting similar temperatures. I might beef that up to 1W as well. Just below that resistor in the image you can see R337, 3.3 Ohm, which is already 1 W.

Finally in front of the EQ board we have R309 3.9 kOhm, 1/4 W, which reaches 42 C (not really a concern). The other warm resistor, to the right, is R310 3.9 kOhm, 1/4 W at 39 C (again, not really a concern).

 

[GPS16]

Hi Smurfer,
the hot resistors in question should be dissipating around 0.2 W. On the large diagram in the manual it states that all resistors are 1/4W unless otherwise stated. If these are 1/4W ones then I think, as you are upgrading the caps, these resistor which are getting a bit cosy may benefit as well. They should be Ok as they have last 30yrs so they cannot be that stressed. It is just from past experience on machine maint, the hot components could have an adverse effect on the PCBs long term. If this discolours then there may be problems with track bonding, PCB becoming brittle and crumbling........ From your photos the PCBs don't look to be affected by long term high temp devices. I am going off experience of the effect of PCBs running for 24/7 industrial duty, on domestic, intermittent use again you should be OK. Beware that if you go up to 1W resistors, you made need to drill the PCB holes as the wires on 1W resistors may be a thicker gauge due to the extra mechanical strength required to support the larger device. May be 1/2W would be a better choice. Up to you!!!

Like the IR camera. Again these are used at work for detecting bad joints on power delivery boxes where there are contactors/circuit breakers passing 20 amps and higher. Bad joints on these set of fire alarms and we all end up in the car park!!!

GPS16

 

[smurfer77]

Okay so I remeasured after letting the machine idle switched on for longer and made sure I reached steady state temperature. The values reported above changed (went up) slightly from what I reported previously. Rough power dissipation expected also noted below (as GPS16 said in last post, it's about 0.2 W in the two hottest resistors on this board).

R334, 3.3 kOhm, 1/4 W. 57 C. 0.19 W
R332 3.3 kOhm, 1/4 W, 54 C. 0.18 W
R309 3.9 kOhm, 1/4 W, 43 C, 0.13 W
R310 3.9 kOhm, 1/4 W 42 C, 0.13 W

Only had some 1/2 W resistors laying around in those values; popped them in today, lifting them from the PCB slightly.

Sadly, the temperatures didn't change at all, but at least they are lifted from the board. Last time I buy vishay/dale resistors - I've had quite a few problems with them in other projects in terms of poor dissipation or resistance values varying more than the quoted amount. Much prefer xicon for 1/4 and 1/2 W, and Ohmite for 1 - 5W.

Here is a pic of the backside of the PCB before and after reflow and silicon coating. Most of the mess, including all the weird scratches, on the before (left) board are actually from the factory believe it or not. The right looks a bit lumpy but the coating was still settling into a flatter layer when i took the pic - click to see the larger version to see what I mean.

Actually, I could use this silicon to 'glue' those big caps to each other and to the board (and will definitely be non-corrosive to the board)...

 

[GPS16]

Hi smurfer,
The large caps don't need to be glued down. Unless you intend bouncing the machine around in the back of a truck. I made the comment to illustrate why they were glued in the first place.

Have you tried the IR camera on the big wirewounds when the machine is running?

That should frighten you!!!!!!

Hence the need for fibre glass sleeving!

GPS16