Calling all Yamaha A-1 Owners. Need Re Recapping Info

theokalat

Active Member
Calling Yamaha A-1 Owners. Recap Info

I have three A-1's, recapped one of them a while back, the other two I acquired for next to nothing from an owner who had previously sent them out to be repaired as they were apparently not working, but they were sent back to owner butchered and in worse state and still not working.

For instance, many lytics were replaced with totally wrong values(some the wrong way around), eg one lytic i found in there was 1000uF in place of original 470uF!

Also found the two 18000uF filter caps were removed and in their place were four 2200uF caps! 2 caps wired together to make a total of 4400uF each pair. Unbelievable.

One of the boards was also a mess, with broken tracks being jumpered with wires and soldering which was an absolute mess.

Just take a look at the attached photos to see what I mean. I have a lot of work here to do by the looks of it.

See photo 3 how this dude attached the two transistors, in the fourth photo how it should be from same board from one of the other A-1's.

Anyway,I need clarification on one of the caps as to their values. In the service manual, C212 is shown in the parts list as 1000uF/50v, but in the schematic it is shown as 10uF/35v.

C212 in the two non working ones are 10/25(though not originals) and in the one I recapped is 10/35.

So my question to anyone who has an A-1, are you able to confirm what the actual value should be.Should it be 10uF or 1000uF?
I tend to think it is 10uF.

The board with the C212 cap is NA07041(power supply board), which is held by a couple of rubber tags at the top and is easily pulled up and out of the amp if need be to check.

Any help here is highly appreciated.
 

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I dunno, the schematic I have doesn't have the value, whereas the parts list says clearly 1000uF/25v for c212. If there's a difference for the australian market, it's not listed in the capacitor values, only in the board part names and fuse values.

Have you checked d202 & d204 for failure? VR201 needs checking, those old pots can get weird.
 
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I have three A-1's, recapped one of them a while back, the other two I acquired for next to nothing from an owner who had previously sent them out to be repaired as they were apparently not functioning properly, but they came to him butchered and in worse state and still not working.

For instance, many lytics were replaced with totally wrong values(some the wrong way around), eg one lytic i found in there was 1000uF in place of original 470uF!

Also found the two 18000uF filter caps were missing and in their place were four 2200uF caps! 2 caps wired together to make a total of 4400uF each pair. Unbelievable.

One of the boards was also a mess, with broken tracks being jumpered with wires and soldering which was an absolute mess.

Just take a look at the attached photos to see what I mean. I have a lot of work here to do by the looks of it.

See photo 3 how this dude attached the two transistors, in the fourth photo how it should be from same board from one of the other A-1's.

Anyway,I need clarification on one of the caps as to their values. In the service manual, C212 is shown in the parts list as 1000uF/50v, but in the schematic it is shown as 10uF/35v.

C212 in the two non working ones are 10/25(though not originals) and in the one I recapped is 10/35.

So my question to anyone who has an A-1, are you able to confirm what the actual value should be.Should it be 10uF or 1000uF?
I tend to think it is 10uF.

The board with the C212 cap is NA07041, which is held by a couple of rubber tags at the top and is easily pulled up and out of the amp if need be to check.

Any help here is highly appreciated.

I have a opened up A-1 here. Its a 10µf /35v chemicon.
 
I dunno, the schematic I have doesn't have the value, whereas the parts list says clearly 1000uF/25v for c212. If there's a difference for the australian market, it's not listed in the capacitor values, only in the board part names and fuse values.

Have you checked d202 & d204 for failure? VR201 needs checking, those old pots can get weird.


Thanks for the tip on D202 & D204. They seem to be rectifier diodes. Is this correct?

I only just started recapping this amp. Most new lytics in, but still need to order a few others to complete the recapping.

So far, apart from the lytics, also have replaced all 10 fuse resistors with new ones, and the 3 pesky vd1212 with two 1N4148 diodes wired in series.
All caps,fusesistors and diodes that I replaced so far have tested within spec. Not bad for a 34 year old amp.

Next will be to replace all 7 pots with bourns multiturn trimpots.
I have the correct Bourns part # for the pots.

Will start checking all components on each board tommorrow. Will see how she goes. Hopefully all other components are good, but I have a feeling that I will find a few fried components on some boards.

There are 4 FET's on a couple of boards, hope they are not fried as they look unobtanium.

IC701, IC702 & IC401, IC402: All 2SK-100 FET's
Don't know how to go about checking these before I finish restoration and power her up, (with a dim bulb tester intially).
 
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Supposed to be, and yet I had to replace one of those cute multi-leg Yamaha rectifer diodes. Just a heads-up to check while you're in there.
 
Just checked them with the diode test on MM. Both checked out good. Relieved. One less component to worry about so far.

Checking each component on boards as we speak. So far so good.

Just need some advise about the 4 outputs on the heatsinks, when I clean them up, do I need to place mica pads between them and heatsink for insulation,and will I need to put any thermal grease?

Haven't dismantled them yet, so not sure what to expect.

Also can I substitute 10uF/35v lytic in C212 with a 10uF/60v as I have some handy here.The voltage a little high so not sure if it would cause any issues down the track.
 
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can I substitute 10uF/35v in C212 with a 10uF/60v for C212 as I have some handy here.The voltage a little high so not sure if it would cause any issues down the track.
Yes..
 
, do I need to place mica pads or will any silpad cut to shape do the job,and will I need to put any thermal grease?
No grease needed with sil-pad.. Grease only needed with mica.
 
No grease needed with sil-pad.. Grease only needed with mica.

Thanks Avionic.

Just some more advise needed, the board in the photo at the top of this thread has broken tracks, and as you can see wires were used to join them.

Am I able to reconstruct the tracks with something like a conductive epoxy pen(about $27-$35 from single pen to 2 part application pen), or are they a waste of money.

Never had any experience with them so not sure if they will work ok.

Or should I leave the wires as they are.
 
That board is a mess.
Never had any experience with them so not sure if they will work ok.
Nor have I.
I would suggest scrubbing it down with acetone.Get rid of that unsightly wire.Get some 18 gauge red enameled wire and redo it neatly. Once you get the board nice and clean,then compare it to the service manuals diagram and make sure to eliminate any undesired solder bridges.
 
That board is a mess.

Nor have I.
I would suggest scrubbing it down with acetone.Get rid of that unsightly wire.Get some 18 gauge red enameled wire and redo it neatly. Once you get the board nice and clean,then compare it to the service manuals diagram and make sure to eliminate any undesired solder bridges.

Already cleaned it up this morning with acetone as you recommended in another thread yesterday.

Came out really clean. I have two other A-1 amps to compare the boards tracks and make sure it all matches up.
 
Already cleaned it up this morning with acetone as you recommended in another thread yesterday.

Came out really clean. I have two other A-1 amps to compare the boards tracks and make sure it all matches up.

Sweet..
 
Finished going through each board, painstakingly checking every resistor, transistor, diode(including the 2 rectifier diodes) and some capacitors that I was able to measure with the DMM. All the above was in circuit testing.

All components measured within spec, except for a few transistors and resistors on some boards that measured erratically(but I suspect this is due to other influences within the circuit causing odd readings).I might pull a few of these out and recheck them just to be sure though.

Also the 4 unobtainium 2SK100 FET's were good in diode test,measuring 0.6v between D-G, and G-S on each side.Well I hope that is what they should measure.

Just waiting on replacement main filter caps, and Bourns trimpots to arrive from supplier to complete the restoration.
 
Got around to doing more testing, started with the problematic power supply board.

After pulling out the parts that measured erratically in circuit, i was able to confirm one fried transistor 2sa872 (TR203)and one failed zener diode wz130(D205)..

The other suspect transistors measured good off circuit so I put them back in.

I can get an exact replacement for the 2sa872 locally.

The diode W130 I believe is a 13 volt zener.
I think it may be a 0.5 watter. Is anyone able to confirm its wattage.

Would something like this be a good replacement:

http://au.element14.com/fairchild-semiconductor/bzx55-c13/diode-zener-13v-500mw/dp/9844490
 
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WZ130---13v/500mw--:yes:
That piece from Element14 will definitely do the trick.:thmbsp:
 
Yes, d202 & d204 are recifier diodes. I had one go on the power board of a CA-600 .

Were yours 1d4b1 as in the A-1?
I cannot see any supplier including digikey has this part number.

Do you have a replacement part number just in case one of these fries in one of my A-1's in the future.
 
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