P2200 Resto - Fools Endeavour

[dondoucette]

I haven’t forgot about this project but as it is of a personal nature it takes a back seat to many other things I have going on.

To that end I have received another parts P2200 and started harvesting, one module looks great the other appears to have been worked on, this is just lazy and poor workmanship... Have a look...

 

[dondoucette]

Quick question for anyone still reading... I would like to replace VR101 with a multi turn pot, is there a recommended suitable replacement.
Thanks for the help gents.

 

[rcs16]

I have a couple here, in for service, I am not going to change the pots, they seemed okay for me to adjust the bias. It does not have to be exact.
Most multi-turn trimmers have 0.1" lead centers, short leads just enough to stick thu a 1/16' pcb, the ones in your pic look big, so trying to get one to fit might require some wire extensions/ingenuity. measure the lead centers on the existing pots and then see if they make them like that anymore.

 

[dondoucette]

My pots seem fine also, but the plastic is 40ish years old and I would rather replace it now while I’m working on the amp and I just thought a multi turn would be convenient for adjusting, it’s not necessary, but I do want to replace the pots with a new quality part.

 

[rcs16]

Then start by measuring the pins spacings, it would be mm. they are usually 5,7.5,15mm spacings.
Did you change the old binding posts? one of the reasons the ones I have are in for service?

 

[amr2]

Multiturn: 3299P-1-102LF or 3296P-1-102LF

 

[amr2]

You have to bend the pins

 

[dondoucette]

No not yet, what little free time I have right now is centred around the amplifier modules themselves, this is a P2200 from my parts stash for personal use only so the posts will most likely be an upgraded part as well.

Did you change the old binding posts? one of the reasons the ones I have are in for service?

 

[dondoucette]

Multiturn: 3299P-1-102LF or 3296P-1-102LF

Thanks...

 

[rcs16]

PV36 is a lower cost alternative.

 

[dondoucette]

Woo hoo
Digikey order
I get one or two orders from Digikey per week, amazing service!

 

[EngineerNate]

What kind of fancy caps did you choose? Cool colors.

 

[dondoucette]

Just some Nichicon caps for stock, the orange axials are EPCOS 220μF 63v (C110 on the Yamaha P2200/01))

Ok gentlemen I could really use some help here, finally getting back to my project.
I tried powering up this module under repair and was getting a positive DC voltage on the output that basically tracks the B+ within a few volts, I shut the variac off at 30volts and removed the new output transistors.
Now when I power up the amp I can turn up the voltage without worrying about what might get damaged.

With an FLIR gun I measured 35+C on R119, R120, R121 and R133. B+ was only 50v, ambient temperature is 18C
Everything else on the board didn’t look to be getting warm, still DC at the output.

Before I start pulling more parts to test should I be looking at D105, WZ-061 can’t find reference on that part not sure what voltage it is.

Thank you for any insights you can share, help is greatly appreciated.

 

[rcs16]

O'h boy from what you are writing, I can tell you are over your head.
WZ-061 is a 6.1V/500mW zener, it provides the bias to the VAS cascode bjt Tr109. The voltage is printed on the schematic.

Word of advise, you would be surprised how far you can get troubleshooting with the ohmmeter/DMM, without ever having to apply power.
Until you can get both channels to measure close to the same on the ohmmeter, there is no sense applying power.
You can compare each connection to ground, you can compare reading across components.
It is called "method of comparison"
Once you are confident, and tired of checking, then apply power, Check your bias voltages against the schematic.

 

[SansuiSteve]

This is a really informative thread. Just made a bid for buy it now on a p 2200. If it goes through I will keep you updated on my progress.

 

[Mrvintage]

Just have to add my input here rcs16 knows his stuff Rick repaired two of my P2200's that Ive had since new (1978) and they work flawlessly now. Thanks Rick for all your work on my babies. I've since bought 3 more P 2200's and one P 2100 which you will get soon to to refurbish

 

[SansuiSteve]

No joy. Got my eye on a couple of P-3500's to take it's place.