Hints on recapping

[_mano]

Hi folks,
Have a TU-719 and AU-919 from new. Have not switched them on in months and was thinking of ebay'ing it, until I saw this forum and realised why I need to hang onto these unique creations.
So, had a peek at the TU-719, and sure enough, there is glue around the caps on the PSU board, and suspect lot more on the AU-919.
Want to start easy TU-719, so some hints on what I need to do will be useful.
a) I understand time and patience is essential.
b) I can use a soldering iron and remove and replace components.
c) have good knowledge of 70s technology and components.
now the brain teasers.
1) Should I totally disconnect the board from the chassis to get a good handle on the board, given if I was to do this, it makes it easier to work on the board, however I will be disconnecting a lot of connecting jumpers by de-soldering etc.
2) Should I do the above board by board clean and update the caps and reconnect, silly question, but experience and thoughts from who have done this before will be welcomed.
3) Should I order all the caps, before starting, or do it per board as I dismantle. Trying to confirm the values of the component while on the board or in the chassis is difficult, if I am to pre-order.
4) In most posts, recommendation also to recap the black flag capacitors, could not find a reason as to why the diodes in serial are being changed, such as MV12, MV103. No issues with changing Zenar diodes.

any hints or pointers to other post detailing the approach would be kindly appreciated.

 

[nosirrah]

Welcome to AK, especially the Sansui forum.
First, take pics, lots of them, then decide how far your recap should go.
At a minimum, do the power supplies.
The experts will be along shortly.

 

[Hyperion]

In my book 're-capping' is one thing and 'reconditioning' is another - read on...

Hi folks,
Have a TU-719 and AU-919 from new. Have not switched them on in months and was thinking of ebay'ing it, until I saw this forum and realised why I need to hang onto these unique creations.
So, had a peek at the TU-719, and sure enough, there is glue around the caps on the PSU board, and suspect lot more on the AU-919.
Want to start easy TU-719, so some hints on what I need to do will be useful.
a) I understand time and patience is essential.

Good, you'll need it

b) I can use a soldering iron and remove and replace components.
c) have good knowledge of 70s technology and components.
now the brain teasers.

Good soldering skills essential, good 70's knowledge very useful.

1) Should I totally disconnect the board from the chassis to get a good handle on the board, given if I was to do this, it makes it easier to work on the board, however I will be disconnecting a lot of connecting jumpers by de-soldering etc.

Play this by ear, sometimes it is essential to remove - other times you can get away with leaving it wired up. If there is any suggestion of damaging a board or something around it by NOT removing it - then you know what to do.

2) Should I do the above board by board clean and update the caps and reconnect, silly question, but experience and thoughts from who have done this before will be welcomed.

Some do this, so they can check their work on a board by board basis, it can provide a very interesting insight into what part of the amplifier makes the most improvement when reconditioning. I use the word 'reconditioning' deliberately - if you simply 're-cap' you are only doing half of the work you should.

3) Should I order all the caps, before starting, or do it per board as I dismantle. Trying to confirm the values of the component while on the board or in the chassis is difficult, if I am to pre-order.

No it isn't - you should be able to discern all the existing component values by close inspection of the boards - do this first and order accordingly (ask here if you are not sure) - do not use the schematic diagram as a component ordering guide, Sansui are notorious for having component values in working equipment which is not the value on the schematic.

4) In most posts, recommendation also to recap the black flag capacitors, could not find a reason as to why the diodes in serial are being changed, such as MV12, MV103. No issues with changing Zenar diodes.

DO change the black flags - it is a MUST DO, replacing with Mica or Ceramic (NP0/C0G) equivalents is valid. Leave the MV12 and MV103s alone unless proven faulty, only the VD series dual diodes are known to be 'flakey' and are usually changed for series pairs of 1N4148's. Zener diodes can go noisy with age - you don't have to change them but treat them with suspicion, especially if you experience noise problems.

any hints or pointers to other post detailing the approach would be kindly appreciated.

Do not re-cap / re-condition your whole tuner - unless you have access to alignment services. Just do the PSU and leave the rest until you have access to/can afford, a proper re-alignment.

Do a search for 'AU919' in the AK search facility - loads of threads (including mine) in there.

Good luck.

 

[naderpe]

Hints…lather your hands with a hand cream before touching any electronics. This can keep ESD problems down if you don’t wear a ESD sensitive strap

 

[_mano]

Thanks for the welcome nosirrah and advise on plenty of pictures and use of ESD from naderpe. John's (Hyperion) suggestion of just doing the PSU on the Tuner to start will be taken fully on board and see then how it powers up. Tiny step at a time.

Any idea on the sourcing of the clear nylon cable tube used for keeping the wire bundle tidy. I can use nylon cable tie, however, would be nice to use the original method.

 

[AUD101]

_mano - welcome to the forum - good to see another UK member here

Any idea on the sourcing of the clear nylon cable tube used for keeping the wire bundle tidy. I can use nylon cable tie, however, would be nice to use the original method.

I've been searching for the very same (or similar) but so far have been unsuccessful :tears:
I think the the only forum member who has been successful is Kale - I do hope he has a look at this thread and can help etc.

Keep the forum updated with your progress - There are plenty members here who will always help you out should you have any questions, problems etc.

 

[ghazzer]

Consider the pin spacing on the PCB when ordering replacement caps. Newer caps are usually smaller than the originals. If the plated holes in the PCB are 8mm and the replacement cap has a 5mm pin spacing, you will have to dog-leg one or both of the pins to fit. Check the characteristics of the available replacements with the same capacitance. You may be able to find one in the next higher voltage level (80v vs 63v) that is a closer match to the original pin spacing.
.

 

[skippy124]

_mano - welcome to the forum - good to see another UK member here


I've been searching for the very same (or similar) but so far have been unsuccessful :tears:
I think the the only forum member who has been successful is Kale - I do hope he has a look at this thread and can help etc.

Keep the forum updated with your progress - There are plenty members here who will always help you out should you have any questions, problems etc.

Try your local craft shops -

for example

http://www.craftdirect.com.au/catalog/product_info.php?cPath=224_226&products_id=2796

Cheers

John

 

[_mano]

Try your local craft shops -

for example

http://www.craftdirect.com.au/catalog/product_info.php?cPath=224_226&products_id=2796

Cheers

John

Cheers John, I'll have a browse in UK, failing that I'll get my brother in AUS to get it and ship it here.

Making progress, on the TU719, removed all the caps on the PSU board, Glue seems to have been applied just around the base of the caps. Cleaned most of it, now ordering the caps mostly Nichicon KL or Panasonic FR's.
As suggested by ghazzer, will be wary of the pin spacing on the new caps. Also, I may just order 5 of 10uF at 25v, rather than 2 at 16V, and 3 at 25V, similar physical size.
The service manual for the Tu-719 does have a parts list which does not show the capacitors for any of the boards. A little challenge to ensure, double check the values against the schematic.

 

[Hyperion]

Cheers John, I'll have a browse in UK, failing that I'll get my brother in AUS to get it and ship it here.

Making progress, on the TU719, removed all the caps on the PSU board, Glue seems to have been applied just around the base of the caps. Cleaned most of it, now ordering the caps mostly Nichicon KL or Panasonic FR's.
As suggested by ghazzer, will be wary of the pin spacing on the new caps. Also, I may just order 5 of 10uF at 25v, rather than 2 at 16V, and 3 at 25V, similar physical size.

Perfect.

The service manual for the Tu-719 does have a parts list which does not show the capacitors for any of the boards. A little challenge to ensure, double check the values against the schematic.

An irritating habit of Sansui manuals - just as well really as the values of the components installed now are what is important.

 

[_mano]

The Tuner TU-719 is now up and running. Changed all the Caps on the PSU and some of the Caps on the power rails on the tuner board and toggle switch board. No sparks or burning smell for 30mins. The initial issue which made me suspect something was going wrong inside the Tuner was when the test-tone stopped working. When I checked it couple of years ago, I stopped going any further once the transistor checked out ok and still no test tone. Did not suspect it could be the capacitors around the oscillator circuit.
All works now, since the change of the electrolytic and the tantalum caps around the transistor.
Couple of pictures of the tuner on the kitchen table, with and without flash.

Now the AU-919, will open up this weekend and make a start, however a quick check of caps from the schematic and service manual parts details is just going over £100 so far. £60 pounds just for the Oval capacitor refurb.

 

[ghazzer]

It's a good feeling to have gotten it working again.

Have you tried looking at other sources for your replacement caps? The main caps are the highest cost and may be OK, so I wouldn't buy replacements until you have them checked out. They may need to be re-formed first if the AU-919 has been sidelined for a while.

 

[madmonda]

Sounds like your getting a grasp fairly quickly. Take your time and always double check your polarities with the orientation of the cap removed. Also, the power supply board is especially a pain in the butt. It can be removed enough without having to remove the wiring. I only had to disconnect 2? wires for me to gain enough access on my 517 and 719 recaps.

I did a lot of AK reading and took LOTS of photos.

 

[_mano]

It's a good feeling to have gotten it working again.

Have you tried looking at other sources for your replacement caps? The main caps are the highest cost and may be OK, so I wouldn't buy replacements until you have them checked out. They may need to be re-formed first if the AU-919 has been sidelined for a while.

Agree, its a good feeling. Checked the prices of caps and availability at rs,farnell,hfc,mouser and settled for mouser as a single shop for convenience. The AU-919 with the tuner has been on the side for more than 2 years and while I am in there will try and make it last another 30years, hopefully.

Sounds like your getting a grasp fairly quickly. Take your time and always double check your polarities with the orientation of the cap removed. Also, the power supply board is especially a pain in the butt. It can be removed enough without having to remove the wiring. I only had to disconnect 2? wires for me to gain enough access on my 517 and 719 recaps.

I did a lot of AK reading and took LOTS of photos.

Absolutely,

approach:
Lots of pictures,
audit visually/electrically each board to capture actual values and make a list / board.
May be order up potential replacement parts. ???
Refurbish board at a time, start with the PSU section and work back from the output stages to the input stages.

Lets see when I open up the box...

 

[_mano]

Well spent well over 24 hours over the weekend taking apart the AU-919. I was going to work through board at a time, however it ended up all the board were removed from the chassis, on each board was emptied of of Electrolytic caps and Black flag caps. Addition to this any Zener over 12V was removed with some of the multi junction diodes. All of the components removed were kept in multi compartment tray with a label to indicate which board it came from.
Also, all the transistors with heatsink were cleaned and reapplied with fresh white goop. Had to dismantle the front and back plates to reduce the number of wires that needs to be unsoldered. All unsoldered and unplugged leads were labelled and plenty of pictures.
Only noticed couple of capacitors on one of the boards was incorrectly silk printed and one value was incorrect on the protection board compared to the schematic.
Ordered the caps today.
When I get some time, while I wait for the caps and diodes, I will ESR the caps to check what % are duff. Also, majority of the time was spent cleaning the glue and there were definitely some green bridges being made on 3 boards.
Checked all of the resistors touched by glue overspill to make sure their values are correct and don't show sign of being cooked.
I have not opened up the Oval caps yet, once I go through the ESR checks on the others, I may decide then.

I did loose concentration at not take a picture of the output transistors when I dismantled the output stage and for some reason I imagined that all the 2SA were on one side and 2SC on the other side. However, following the positive and negative rail into the Heatsink and beeping out the collector connection confirmed what needs to be where. At this point I called it a night and went to sleep as I did not want to tempt fate.

And I hate that glue..

 

[Hyperion]

Only noticed couple of capacitors on one of the boards was incorrectly silk printed and one value was incorrect on the protection board compared to the schematic.
Ordered the caps today...

Note well: The capacitor values installed NOW are the correct ones :yes: - the schematic is wrong :yes: - not the installed capacitor

And I hate that glue..

Join the club

 

[_mano]

Note well: The capacitor values installed NOW are the correct ones :yes: - the schematic is wrong :yes: - not the installed capacitor



Join the club

Thanks Hyperion, agree the installed cap on the board is correct.

 

[Kale]

Any idea on the sourcing of the clear nylon cable tube used for keeping the wire bundle tidy. I can use nylon cable tie, however, would be nice to use the original method.

I found that nylon tube somewhere on the net, but it was year or two before, so I lost that source.
But if you want, I can send you 2m of that nylon tube. It is really good, because you can tie cables very strong without to broke that nylon tube.
So, give me yours address on PM, and I will send you 2m for free.

 

[_mano]

Kale,
Very kind of you, I also have requested my brother in Australia to send me a sample from the hobby shop over there. Cannot find anything this side in UK. Looks like your inbox for the private message is full and not accepting any further PM. If you are happy, send me a pm with your email address and I can reply.

Just send an email instead of a PM

 

[_mano]

Progress update:
Removed and replaced all the electrolytic Caps, diodes, black flag caps, all the goop refreshed and all the boards are back in the Amp. Have not touched the Oval caps yet as they test good enough for initial board power-up and checks.
Went through all the Caps tested with LCR and ESR meter, roughly just over 10% of the caps on each board are out of spec, ie.. high ESR or Capacitance value 20% off the mark.
On the main Oval caps, (15000uF), ESR is low around 0.33 to 0.47Ohm and cap value between 12000uF to 13500uF.
This weekend, will put the original Oval caps back in, and will power up the pre-amp section first, check the voltages and trim as needed. If it all goes well, then to driver stage etc.. If it all looks and feels sweet, then I will start on the oval caps.
Have been checking and double checking all the connections, polarity and any solder bridges/splashes with the meter and magnified glass.
Trying not to rush...