M44 cap question

[Seanram]

I just picked up this nice looking amp.
The internals look good and untampred with.
Didn't test it yet but couldn't pass on the deal (€35).
As you can see I'm currently working on the cap replacement.
So now my question:
-Should i also replace the big blue railcaps?.

[Eric D]

I wouldn't. Replacing those does more harm than good, especially on the M44 which has a very fragile board.

[Seanram]

Thank you for the fast reaction!
Would it be wise to check for leakage (the PS cap had leaked a fairly amount of fluid)?
Or are the big ones less sensitive for leakage?

[trickyricky]

The hfq and other hf capacitors will or have already leaked. The recommended replacement is the fc series. Do as Eric stated and leave those big rail (light blue) caps alone.

Zapco ZxxxS2 amplifiers use the hfq on both the rail and dc filter sections and all of them leaked. Some causing damage to traces and via holes. Just finished 5 of them and trust me all of them leaked.

[Eric D]

The hfq and other hf capacitors will or have already leaked. The recommended replacement is the fc series. Do as Eric stated and leave those big rail (light blue) caps alone.

Zapco ZxxxS2 amplifiers use the hfq on both the rail and dc filter sections and all of them leaked. Some causing damage to traces and via holes. Just finished 5 of them and trust me all of them leaked.

It is nice to know these problems are not just limited to PG amps. I know of a few people who switched from PG due to the leaking cap problem, in their mind blaming PG for it. I have a lot of respect for Zapco, especially their older product, and with them having similar issues it just makes me all the more confident in PG.

[zeropoint0.5]

Thank you for the fast reaction!
Would it be wise to check for leakage (the PS cap had leaked a fairly amount of fluid)?
Or are the big ones less sensitive for leakage?

Only the 4 ps caps leak... just follow Eric's advice......

if you wanna change something that makes sense, replace both resistors under the right blue railcap,

maybe you see already discoloring, replace them with a 5W, same value 91ohm, and place them 1/2 inch away from the board.....

I've done it on all of my (8) m44 boards.... on none of them i touched the blue railcaps......

[trickyricky]

The hfq and other hf capacitors will or have already leaked. The recommended replacement is the fc series. Do as Eric stated and leave those big rail (light blue) caps alone.

Zapco ZxxxS2 amplifiers use the hfq on both the rail and dc filter sections and all of them leaked. Some causing damage to traces and via holes. Just finished 5 of them and trust me all of them leaked.

It is nice to know these problems are not just limited to PG amps. I know of a few people who switched from PG due to the leaking cap problem, in their mind blaming PG for it. I have a lot of respect for Zapco, especially their older product, and with them having similar issues it just makes me all the more confident in PG.

Yeah it's a problem with those series and that's why they where discontinued. Now every amp i get for repair our service i make sure i remove those hf series caps.

[IsakAlexander]

I went ahead and replaced everything(one 100uf not changed in picture). The blue ones were around 8000uF. Cheap replacements more like 10500ish. Might power it up this weekend. Just need to sort out the missing traces around the burned resistor area.

[freshkryp69]

I just picked up this nice looking amp.
The internals look good and untampred with.
Didn't test it yet but couldn't pass on the deal (€35).
As you can see I'm currently working on the cap replacement.
So now my question:
-Should i also replace the big blue railcaps?.

Welcome to the forum!

I replace the rail caps on every PG amp, but thats me.. You seem confident in replacing the power supply caps, and ya got the amp apart Id say if you have some experience soldering wires, replacing caps etc you might as well replace the big blue rail caps with some Panasonic TSHA series or Elna capacitors, they have a great track record for audiophile caps!

Beware though many people have seriously screwed up which is why 1 of the most experienced amp techs on this forum said to leave them in due to the fragile circuit board that can allow the thru-holes and pads to pull out. Its better if 98% of people leave them in as the PG rail caps have a good reputation of lasting many years and sound fine. Better performing caps have been made since this amp so its up to you...if you have the skills.

[freshkryp69]

I went ahead and replaced everything(one 100uf not changed in picture). The blue ones were around 8000uF. Cheap replacements more like 10500ish. Might power it up this weekend. Just need to sort out the missing traces around the burned resistor area.

What brand and model did you use, are they 105c rated??

[IsakAlexander]

Nichicon FG, 85c only but this amp will never be driven hard ever again Should have used KA series maybe but I like the gold look on these.

[zeropoint0.5]

I went ahead and replaced everything(one 100uf not changed in picture). The blue ones were around 8000uF. Cheap replacements more like 10500ish. Might power it up this weekend. Just need to sort out the missing traces around the burned resistor area.

nice job indeed, but why did you not replace the two resistors of 91 ohm underneath the right big rail cap ??

I always replace those with a 5W same value 91ohm model and 1/2inch away from the board....

those don't get got, they COOK and are a fragile part in the whole amp !!!! you see in most M44's the discoloring on the backside of the board

due to the heat caused by them.....

[zeropoint0.5]

I just picked up this nice looking amp.
The internals look good and untampred with.
Didn't test it yet but couldn't pass on the deal (€35).
As you can see I'm currently working on the cap replacement.
So now my question:
-Should i also replace the big blue railcaps?.

they look just fine !!!! leave them in for sure... i have 8 m44 boards, i didn't replace them on any amp.......

i personally would advice you like i posted before, to replace the two resistors of 91 ohm underneath the right blue railcap

with a 5W same value 91ohm resistor and 1/2 inch away from the board..... this is the smartest thing you can do along with the

4 ps caps to replace.... i also always replace every little cap only when the isolation is shrinked... if they look fine, i leave them in.....

But of course it is a personal preference to replace all the caps of the whole board or not.... i don't do it.... that's my descision......


By replacing the rail(or other) caps, you need a good desoldering station along with the skills....( train first on an old television or something)

please check all the via's for conductivity BEFORE you solder in new caps.... if nescessairry, you can repair them...... if you don't do this,

you'll create a mess !!!!


for the rest, 35 bucks !!!!!! well that's a hell of a deal for sure .........


take the right descisions and good luck......

[IsakAlexander]

I did not solder in the resistors yet due to missing traces... Previous owner removed one of them and took the circuit trace with it

[zeropoint0.5]

I did not solder in the resistors yet due to missing traces... Previous owner removed one of them and took the circuit trace with it

strip a FTP kable and you will find some gold looking wires of about 0.2mm you can perfectly use to replace/repair a ripped trace......

[Seanram]

Thank you all for your reactions,

I have quite à bit experience in soldering (i'm a electrical engineer of profession).
During the period i was At school is used to repair amps for some extra bucks.
Now i'm only buying broken down PG amps or high power amps so i can hopefully revive them (it can also be s cheap way to collect rare amps).

so back to THE M44 i tested it last week and it sounds excellent!.
Also order à few 91 ohms 5 W resistors and Will upgrade as soon as They arrive.

I have been reading this forum for years now and only had THE guts à few months ago to join.
There is allways more to learn for this forum and its members.