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Accuphase P-260 repair & restoration (help)

wolfy

wolfy

New Member
Hello everyone!

I would like to restore my dad’s 1979 Accuphase P260. The amplifier has had a rather hard life. As of today, it is not fully functional.

The amplifier’s history:
  • It was bought in the 80’s as fully functional.
  • In the 90s, the amplifier got water damaged; it was repaired: the two big (40 000uF) filter capacitors were replaced with 8x 10 000uF capacitors. The relay on the right was also replaced.
  • In the 2000s, the amp was lent to my dad’s brother, who broke it by attempting to clean it.
  • The amplifier was attempted to be repaired by many “technicians” who worsened the condition. It was said to be irreparable, because there was no schematic available at the time. My dad then gave up on the amplifier and put it aside.
  • Few years ago, the schematic of the P260 appeared on the hifiengine.com. I managed to convince my dad to get the the amplifier fixed.
  • We handed the amplifier over to a technician who replaced all the electrolytic capacitors with YAGEO capacitors; The filter caps were also replaced with Nippon Chemi-Con 2x 47 000uF 80v. VR1, VR2, VR3 trim pots were replaced on both channels.
  • After the amplifier was “repaired”, it seemed to be working fine! BUT, after few undefined minutes/hours, the sound out of the left channel came out very VERY distorted and soon after the circuit protection shut of the amplifier.
  • The technicians thought the output transistors were the cause, so all were replaced with SEMELAB: BUZ900 & BUZ905.
  • The issue remained, the sound out of the left channel was still coming out very distorted after a certain time and the circuit protection kicked in.
  • The amplifier was once again returned as irreparable.
  • Then, it was then given to a family friend who found out that the LEDs on the left channel caused the amplifier disfunction. After replacing the LEDs (D3 & D4) on the left channel only, the amplifier was finally repaired and worked well for couple of years.
  • Few days ago, the Accuphase P260 had developed a problem. The sound out of the right channel comes out distorted (reminds of a dying tweeter), but the circuit protection doesn’t kick in. The left channel works fine.
I am very attached to this amplifier. I grew up with it sitting broken in the living room acting as sculpture. Ever since my early teen years I’ve wanted it to work!

Now that I am a little older, my dad gave the amplifier to me; he knows how much I like it.

What I’ve done so far:
  • Check the DC offset on both channels.
  • The DC offset on the right channel is very unstable: when the amplifier is first turned on the offset is ~40mV. However, as the amplifier gets warmer, the offset starts dropping, after few minutes it settles at around ~30mV. After letting the amp idle for few hours, the offset drops ~10mV below 0.
  • The DC offset on the left channel seems to be okay-ish I think. It fluctuates between 5mV and -5mV, but mostly it is around 1.5mV. I would like to fix that too. Chase it closer to 0mV and keep the fluctuations at a minimum. But for now, the right channel is a priority.
  • The DC offset was tested with the amp in the normal mode, but similar behavior happens in the CLASS-A operation.
I have a basic knowledge in electronics. I built many small 9v circuits (guitar pedals) and I know how each component in a circuit works and how to use a multimeter.

That said, I don’t know where to start with this repair . . . :(

I never worked on any amplifiers before and have a very basic knowledge of how they work. I am also not too good at reading schematics, especially the more complicated ones. But I am willing to learn, fully repair and restore this amplifier myself.

The first thing I want to do is get the amplifier working properly.

After that, I’d like to:
  • Put the original Hitachi 2SK134 & 2SJ49 output transistors back in, as they are probably working just fine!
  • Replace all the YAGEO electolytics with audio grade capacitors,
  • Replace the relays,
  • Wash it clean,
  • And perhaps have the enclosure repainted / polished.
With all the information I have just given, I was hoping that someone on this forum would be willing to guide me through this repair and help me restore this beautiful amplifier! :)

Throughout the process, I will be taking pictures and perhaps even recording videos for you.

To anyone that read this and / or is willing to help in any way, thank you!

Pictures: https://imgur.com/a/9MiOiH9
Schematic: https://www.dropbox.com/s/2oq0k6q1hi16tz9/hfe_accuphase_p-260_schematic.pdf?dl=0
 
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Love your story this is what makes Vintage Audio so appealing .

Yes would be nice to put your original matched Output transistors back in... which ... might help to balance Left and Right channels .... give them a test.

And if they test bad try to determine whether the previous technicians checked the parts down swim from the output transistors....

There are so many very helpful Gents on here.

l,m new at this skilled trade...and will help with some of the restoration...Check out my two posts : restoration of AKAI AA1175 and AKAI AA5810 where people are kindly helping me out in the right direction .

Have also learnt a lot on YouTube ... my two favourites are ; xraytonyb Great for vintage restoration.... blueglow....
 
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I watched xraytonyb before. I am going to check out blueglow and your posts :)

If the replacement output transistors are working fine, I'll keep them in until I get the amplifier working properly.
So far the only wrong thing with it: is the very unstable DC offset on the right channel.

Do you or anyone else happen to know what could be causing this unstable offset?
 
Have learnt that transistors can Flutter a bit..... and x-ray Tony talks about the importance of matching transistors .... with some marked with paint to indicate that they were matched how true this is I don’t know ...But if you want a balanced system l can see this being relevant.
 
This is the Gent that can smooth out your Audio Woe,s.

Do you remember Citizen Smith 1978 .... Power to the people.... lov it.

He was called Wolfe... Wolfy...LOL.
 
First thing I would do is take it to a reputable tech but if your determined to go ahead check for dry joints on the pcb's, then sort that shoddily replaced relay out.
 
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avionic said:
Welcome to AK Wolfy
Click to expand...
Thank you!

Reliving. said:
This is the Gent that can smooth out your Audio Woe,s.

Do you remember Citizen Smith 1978 .... Power to the people.... lov it.

He was called Wolfe... Wolfy...LOL.
Click to expand...
I never heard of Wolfe :eek:

reddish75 said:
First thing I would do is take it to a reputable tech but if your determined to go ahead check for dry joints on the pcb's, then sort that shoddily replaced relay out.
Click to expand...
There are no reputable techs where I live . . .and how am I supposed to learn if I don't do stuff myself? :p

I am going to check for dry joins.
Since the last issue was resolved by replacing D3 & D4 on the left channel, do you think that I could replace the D3 & D4 on the right channel as well? The LED's on the right channel are still the factory ones.

The two relays are different and do different things.
RELAY 1 is the one that was replaced when it got water damaged:
GXiqszl.png


RELAY 2
QjdKHAy.png


What confuses me is that it doesn't say what relays these are, there is no part number in the parts list.
What relay can I replace the RELAY 1 with so that it screws on like the original?
 
wolfy said:
What confuses me is that it doesn't say what relays these are, there is no part number in the parts list.
What relay can I replace the RELAY 1 with so that it screws on like the original?
Click to expand...
Snap a few photos relay part numbers are usually printed on the relays some where.
 
wolfy said:
do you think that I could replace the D3 & D4 on the right channel as well?
Click to expand...
I'm sure you could.If your soldering/desoldering is half decent.If it isn't. Pick up a piece of junk and practice. Won't guarantee it will solve the problem.:biggrin:
 
avionic said:
Snap a few photos relay part numbers are usually printed on the relays some where.
Click to expand...
This is the relay that replaced the damaged RELAY 1:
vIsC8Su.jpg

avionic said:
I'm sure you could.If your soldering/desoldering is half decent.If it isn't. Pick up a piece of junk and practice. Won't guarantee it will solve the problem.:biggrin:
Click to expand...

My soldering skills are okay. I have a feeling that the relay isn't an issue. So I'll first replace the diodes.

In the schematic, it says:
7nCtA6U.png

I don't understand what TLR120 means. On the amplifier itself, D3 and D4 look like regular 5mm diodes.
Will any 5mm round LED work ?
 
avionic said:
Pretty darn close....
https://www.mouser.com/ProductDetail/Lumex/SSL-LX3044HC?qs=sGAEpiMZZMtmwHDZQCdlqTuYDjnDlInPOtDjYdyfMR4=
Click to expand...
I have 5mm LEDs in stock that fits the specs. I'll replace them this week.
avionic said:
Do you know what they are supposed to look like ?
How are they supposed to mount to the chassis ?
Click to expand...

I found a person who completely restored an Accuphase P260 amplifier. And he posted A LOT of pictures.
This is the link: http://amp8.com/tr-amp/accuphase/p-260.htm

From the link above I found how the relays are supposed to look like:
p260-11k.jpg
 
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