500 TX sigh.....

CT Jim

AK Subscriber
Subscriber
OK, I got my TX back with repairs that were beyond my capabilities, and did mention some characteristics in my thread about a Fisher 500TX score. I have been using it some in my shop while I started making a Chestnut cabinet for it, but it died.... Hum and some static on both channels, not controlled by the volume control?? I'm a little bummed, but hey it's old stuff! Power supply?

So perhaps now is the time I should jump in and rework it because I know it did work? I can handle caps replacement but do not have equipment for other checks, other than a digital tester.

Any suggestions on a path to Fisher nirvana for me?
 
Power supply is a good guess. If you take it apart you may be able to see if the caps have vented. They often do vent but not always when they fail. If you have a multimeter you could also check th dc power supply voltages. How loud is the hum?

I have decided to restore my 500tx next. I will probably start it later this week.
 
Jim, I would do what apple_scruff mentioned first, but also do a quick check on the reverb jumpers.

George.
 
Thank You George!

I am going down to my workshop to open the hood!, and check the jumpers.

This is an old piece, like me :D
 
OK, checked without the jumpers, and the hum is still present? Unaffected by the volume control, but I'm assuming the jumpers for the reverb are the same as a pre/main jumper?? so the issue is in the power supply, I think. Here are a few pics of some "burn" areas as questionable....now I did see some leakage(powder?) on one of the large caps?
 

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Looks to me as if the diode and resistor have already been replaced. I would at the least replace the caps that are buldging and leaking. Honestly I would replace all of the electrolytics.

The reverb jacks are pre volume control. The volume control is the last thing before the pre-driver and output stage. So it is either the power supply or the predriver output section.
 
Interesting. I see one cap leaking somewhat, but do not see others?? Maybe I'm missing something but I still think I want to work on this myself. I have read a lot on AK, learned a lot, and I know that AKers keep on helping, so how bad can I make it :)

I did post for more info on the desoldering wand as well as the solder station. Once I figure out George's list I think I'll jump in, and tackle it myself. Technically I have nothing to lose!
 
Make sure it is not the power knob. The leads on my 440t power switch got corroded so when you click (turn) the power button on nothing happens. The leads on the "pot" on the inside of the chassis on the rear of the power knob are done for in other words. I found the wire coming from the AC source and the black wire going to the power tranny and shorted them together. I use a power strip to turn my 440t on.

The classic symptom are you turn it on, the lights stay on for a second, then the unit just turns off...it does that a few times then will not light up at all.


Power knob failure is a classic Fisher T death rattle....check that before you do anything else.
 
Interesting. I see one cap leaking somewhat, but do not see others?? Maybe I'm missing something but I still think I want to work on this myself. I have read a lot on AK, learned a lot, and I know that AKers keep on helping, so how bad can I make it :)

I did post for more info on the desoldering wand as well as the solder station. Once I figure out George's list I think I'll jump in, and tackle it myself. Technically I have nothing to lose!

Jim, I would start with the power supply board if your going to do the recap. If you have good soldering skills, just take your time, document, take pictures, you can do it.

The list I posted included the caps on the power supply board, along with the 180 ohm resistor that gets real hot, all the diodes, for the rectifier and zeners. The larger rectifier diodes will compliment the 2 larger filter capacitors.

By your pictures, I could't zoom in, but it looked like someone put in a couple of fuses, which is fine, but I would replace them with the fuse holders that mount on the board, that I put on the list.

Hope this helps.

PM me, or post here if you have any questions, or heck, if you'd like, I can PM you my phone number if needed, don't mind at all.

George.
 
George
My soldering skills are ok, maybe not production level, but adequate, so I'm going for it.

I'll place the order tuesday, and as far as I'm concerned, if I'm going to do it, i might as well go for everything it needs.

Thanks for being there, and Larry also!! I swear you guys must sleep with these :)

Thanks
 
The "burning" of the board in the area of the resistors is pretty much normal in the 500TX. As the PS is on the underside AND it's upside down (when the unit is right side up), with little or no ventilation, it's gonna get hot. Those are all factory resistors in it. For 1W and Above FISHER used standard Bradley Allen Carbon resistors. So that board is identical to mine when I opened for the 1st time.

On the subject of the 2 large main caps (1st two off the fuses). The 3rd leg (on the top of the cap) is there just for stability to keep them from flopping around. Take some 2 part epoxy or Hi Heat Glue gun and just glue the new ones down AFTER bending the leads and ensuring they will fit in the holes. That 3rd leg has confused more than a few owners.

The large resistors are 1 W IIRC. To cut down on the heat from them mount at least 1/2" away from the board. But no higher than the bottom plate. you could put in a 2W resistor and mount the same and it will also do the job, just not get as hot.

The caps are definately toast. The 2nd main is starting to puke. That will start it humming.

The Fuses for the 500TX were originally on the EMITTERS of the outputs. FISHER PUT OUT A SERVICE BULLETIN to remove them from the emitters and install 2 pigtail type fuses in the spots shown on your board. So your's has at least the power supply fuse part done. Flip it over and take a picture of the outputs from the amp side. That will tell the rest of the story. Sometimes the shops didn't putt the emitter fuses. If they are there, remove them. It's in the back of the manual on AKDATABASE. www.akdatabase.org/AKview

If you get stuck, post up and we'll be here to kibbutz :D . When it's running right, it's a damned good rig. It just needs a good tuneup.

GEOKOST: Good list. I would make one suggestion. On the lytic signal path caps, I would have used UKL series vs. the UPW. A bit less noise, and lower leakage. about the same price. Everything else is fine. Pretty much mirrored what I put in mine. Other than the tuner problem I'm having In manual mode FM, which I hope to get to after the TA-600, It's never given me a days worth of trouble.

Good Luck Jim.

Larry
 
On the lytic signal path caps, I would have used UKL series vs. the UPW.

Oh boy, you have to tell me which ones those are on the list under which section!

I already have pics of the other side, but they're on my other computer. Will post them later today!

Thanks
 
George; You did good. It'll run fine as is. You might have a little more quiesant noise floor but it's not a deal breaker. I just looked at mine and it's pretty much the same. Mainly UPW's and it's pretty quiet. However over the years working on Pioneers you tend to learn a few tricks and that's what i did here with your list. Overall the noise floor probably won't be audible, but it will be visible from a scope.

Jim; Basically from the EQ board thru the outputs are UKL's (provided they are radials - both leads on the same end). The SUB 4.7uf's I substituted ECQ Stacked films for the lytics. Work better than lytics and cut the noise floor down even more.

POWER SUPPLY BOARD:

1 512-1N4751ATR 30V 1 WATT ZENER DIODE
5 512-1N5408 3 AMP RECTIFIER DIODES
2 863-1N5929BRLG 15V 3 WATT ZENER DIODE
1 647-TVX1V102MCD 1000UF 35V AXIAL LEADS
1 647-TVX2A471MCD 470UF 100V AXIAL LEADS
2 647-UPW1H221MPD 220UF 50V
3 647-UPW1H101MPD 100UF 50V
2 647-UVZ1J332MRD 3300UF 63V OK!
2 693-0031.8231 FUSE SOCKET
2 576-0313005.MPX 5 AMP 250V LITTLEFUSE CARTRIDGE FUSE
1 594-5083NW180R0J 180 OHM, 2 WATT RESISTOR


MUTING BOARD 2059-1:

1 647-UPJ1A561MPD6 560UF 10V....................(*) 647-UPW1E561MPD
1 647-UPW1V270MDD6 27UF 35V....................OK No 27 uf in UKL You could bump up the value to 33uf


PREAMP BOARD 2019-4:

2 647-UPW1HR47MDD .47UF 50V.................(**)667-ECQ-U2A474ML
2 647-UPJ1A561MPD6 560UF 10V..................(*)647-UPW1E561MPD
2 647-UPW1V4R7MDD 4.7UF 35V...................(*)647-UKL1H4R7MDD1AA


AUDIO FILTER SELECTOR BOARD 2028-1:

1 647-UPW1V101MPD 100UF 35V...................(*)647-UKL1H101MPD

AUDIO CONTROL AMP 2024-1:

6 647-UPW2A010MDD 1UF 100V....................(**)667-ECQ-E1105KF
2 647-UPW1V4R7MDD 4.7UF 35V...................(*)647-UKL1H4R7MDD1AA




POWER AMPLIFIER MODULE BOARD 2175-1:

2 647-UPW1V101MPD 100UF 35V...................(*)647-UKL1V101KPDANA
2 647-UPW1C560MDD 56UF 16V....................(*)647-UPW1E560MDD
2 647-UPW1V4R7MDD 4.7UF 35V....................(*)647-UKL1H4R7MDD1AA


2 647-UPW2A010MDD 1UF 100V........................(**)667-ECQ-E1105KF
1 647-TVX1H102MCD 1000UF 50V AXIAL LEADS...........(***)647-UKL1H102KHD
__________________


(*) If UPW bumped the voltage up 1 step or no UKL in this value/voltage. 100uf 35V is an 85* which is ok here. But not on Power supply. Mixing 1 or 3 in the signal path is not detrimental. It'll still sound better than it does now, with a lot lower noise floor.

(**) Sub 4.7uf are replaced with stacked film ECQ's. Way better than a lytic.
the 1uf 100V might have a clearance problem. Just insulate the longer leads.

(***) OPTIONAL Radial. Up to you whether you use this or TVX.

Larry
 
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George; You did good. It'll run fine as is. You might have a little more quiesant noise floor but it's not a deal breaker. I just looked at mine and it's pretty much the same. Mainly UPW's and it's pretty quiet. However over the years working on Pioneers you tend to learn a few tricks and that's what i did here with your list. Overall the noise floor probably won't be audible, but it will be visible from a scope.

Jim; Basically from the EQ board thru the outputs are UKL's (provided they are radials - both leads on the same end). The SUB 4.7uf's I substituted ECQ Stacked films for the lytics. Work better than lytics and cut the noise floor down even more.

POWER SUPPLY BOARD:

1 512-1N4751ATR 30V 1 WATT ZENER DIODE
5 512-1N5408 3 AMP RECTIFIER DIODES
2 863-1N5929BRLG 15V 3 WATT ZENER DIODE
1 647-TVX1V102MCD 1000UF 35V AXIAL LEADS
1 647-TVX2A471MCD 470UF 100V AXIAL LEADS
2 647-UPW1H221MPD 220UF 50V
3 647-UPW1H101MPD 100UF 50V
2 647-UVZ1J332MRD 3300UF 63V OK!
2 693-0031.8231 FUSE SOCKET
2 576-0313005.MPX 5 AMP 250V LITTLEFUSE CARTRIDGE FUSE
1 594-5083NW180R0J 180 OHM, 2 WATT RESISTOR


MUTING BOARD 2059-1:

1 647-UPJ1A561MPD6 560UF 10V (*) 647-UPW1E561MPD
1 647-UPW1V270MDD6 27UF 35V OK No 27 uf in UKL You could bump up the value to 33uf


PREAMP BOARD 2019-4:

2 647-UPW1HR47MDD .47UF 50V (**)667-ECQ-U2A474ML
2 647-UPJ1A561MPD6 560UF 10V (*)647-UPW1E561MPD
2 647-UPW1V4R7MDD 4.7UF 35V (*)647-UKL1H4R7MDD1AA


AUDIO FILTER SELECTOR BOARD 2028-1:

1 647-UPW1V101MPD 100UF 35V (*)647-UKL1H101MPD

AUDIO CONTROL AMP 2024-1:

6 647-UPW2A010MDD 1UF 100V (**)667-ECQ-E1105KF
2 647-UPW1V4R7MDD 4.7UF 35V (*)647-UKL1H4R7MDD1AA




POWER AMPLIFIER MODULE BOARD 2175-1:

2 647-UPW1V101MPD 100UF 35V (*)647-UKL1V101KPDANA
2 647-UPW1C560MDD 56UF 16V (*)647-UPW1E560MDD
2 647-UPW1V4R7MDD 4.7UF 35V (*)647-UKL1H4R7MDD1AA


2 647-UPW2A010MDD 1UF 100V (**)667-ECQ-E1105KF
1 647-TVX1H102MCD 1000UF 50V AXIAL LEADS (***)647-UKL1H102KHD
__________________


(*) If UPW bumped the voltage up 1 step or no UKL in this value/voltage. 100uf 35V is an 85* which is ok here. But not on Power supply. Mixing 1 or 3 in the signal path is not detrimental. It'll still sound better than it does now, with a lot lower noise floor.

(**) Sub 4.7uf are replaced with stacked film ECQ's. Way better than a lytic.
the 1uf 100V might have a clearance problem. Just insulate the longer leads.

(***) OPTIONAL Radial. Up to you whether you use this or TVX.

Larry

Larry, thank you very much for this updated information. Your experience is sure helping me out.

George.
 
OK, guys!

My order is into Mouser!:banana:

What fun combining the two lists....after having the substitute for the 8 out-of-stock (100v 1 uf) I inadvertently still left it on the cart list, called Mouser and the 17 weeks leadtime was confirmed, so I removed it planning on ordering from PE tonite, when I determined I should have simply deleted it. So, I'm good to go when everything arrives.

Then a little planning, and I'll jump in.

One question, do you typically remove the boards one at a time to rework them, or does it depend on access? Some boards are accessible on both sides on some equipment.
 
OK, guys!

My order is into Mouser!:banana:

What fun combining the two lists....after having the substitute for the 8 out-of-stock (100v 1 uf) I inadvertently still left it on the cart list, called Mouser and the 17 weeks leadtime was confirmed, so I removed it planning on ordering from PE tonite, when I determined I should have simply deleted it. So, I'm good to go when everything arrives.

Then a little planning, and I'll jump in.

One question, do you typically remove the boards one at a time to rework them, or does it depend on access? Some boards are accessible on both sides on some equipment.

Jim,

I removed mine one at a time, and ran it, checking that everything was still in working order. After I rebuilt the power supply and I knew I had a working unit.

George.
 
Jim,

Did you substitute the 1uf and 4.7uf for the stacked film ECQ's like Larry suggested?

I know we got to going back and forth between my thread and yours.

George.
 
I usually look for the twist ties o the harness and undo them giving me some slack, then lift the board off the standoffs, and rotate it CAREFULLY to give me access. The POWER SUPPLY board will require you to remove leads from the back side (closest to the back wall) and IIRC the inner side (away from the fuses). All other leads can be left on. Draw a diagram of the board edge, write down the pin numbers and then write down the wire color for that pin. you can remove them and lay them in order along the back wall and the side.

The tone control board will require you to remove the front panel and gain access to the nuts holding the pots to the front fascia. Be VERY Careful with the front panel as the Tune-O-MATIC board is mounted on it. Release the front panel enough to gain access to the IIRC 2 or 4 screw holding the T-O-M board to it, and uncrew it. Then remove the panel and set aside.

Most all of the other boards will requir only undoing the harness twist ties to gain slack on the boards. Lift and rotate.

I did mine 4 years ago so memory is a bit fuzzy, but this is pretty much how I did it. It's enough to get you started, and be able to figure it out.

In any event redo 1 board, then test the unit. If everythig works, go on to the next board, then test. Repeat until done. Don't empty the board of old pieces then put new ones in. Remove one piece at a time and replace immediately.

On the old caps (especially the plastic covered Mallory's) they will be marked + on the top at one side or another. Make a corresponding mark (+) on the board next to the cap. The new caps have a colored line with a unfilled arrow with a - sign in it. This is the Negative side of the cap. The unmarked side is the + side.

With regard to the ECQ Stacked film They are bipolar and it doesn't make a difference which way they go in. If you want the printing facing all the same direction, fine. If not that's ok too.

Resistors and diodes. Irregardless of size I normally don't bottom them out on the board. that's just me. Most will get hot in the power supply. 1/4"-1/2" clearance with the board is sufficient. But note that they do have a tendency to get mushed down or over. A bit of spaghetti tubing on the leads will help keep shorts away. And the gap aids in cooling them. You can bend a small kink in the lead (a V shape) to keep them up while soldering them. Same for transistors.

Larry
 
IT LIVES!! :banana::banana::banana:

With the help here in the Fisher forum, and especially my emails and phone calls back and forth with George(GeoKost) providing some guidance for my cautionary questions, today I fired her up. No Smoke, No Hum, back in business!! OK, I only did the power supply board now.

I probably have 5+ hours involved in doing this power supply board, from picture taking to diagramming to looking closely at every aspect of this board. I imagine someone familiar with repair work could do it in 2. I'm amazed at the small size replacement parts. I found a used Weller solder station and a circuit board holder, both from the same person. Boy, am I glad I got the board holder, spin left, spin right, turn over turn back, etc....just made it so much easier!

So, if I can do it, with some help, I think a lot of people can do the same!! The very hardest part of all this is figuring out how to read the schematic. First it's upside down, then it's backwards. I had to blow it up and print just the PS board, and I still needed a magnifying glass sometimes. Old eyes!

Thanks ALL!

Don't you just love those bananas!!!
 
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