working on cool suitcase stereo.... need help finding parts

[Mikefc]

I'm restoring a MasterWorks suitcase stereo with Garrard TT. All transistors are VFN2745E, I cannot find any specs on these. Does anyone have experience with this ?

 

[regore]

Checked all of my old cross reference manuals and that transistor does not exist ! Are you sure that's the correct number? Model number of your MasterWorks phono? Maybe I can cross reference that number to a SAMS schematic and get a better part number.

 

[century tek]

What is the problem with it? Pics?

 

[Mikefc]

the only other nomenclature on the device is "129 8" , I've attached a pic of the item. The problem is that there is no audio after the first two transistors ( L & R ) which are fed from a Phono/Aux switch selector. Switch works, signals present at output. With out schematic I'm poking in the dark, so these first two transistors seem to be the place to start. As far as model numbers, you'll see in one pic there is a stamped number 420682, on the chassis. This is the only marking of any kind. The name Masterworks is all that is mentioned on the front, that and Garrard on the TT.

 

[KentTeffeteller]

This is most likely germanium transistor equipped. Is the cartridge on the Garrard good (most likely ceramic). Those are known to go bad sometimes or lack output on one channel.

 

[Mikefc]

This is most likely germanium transistor equipped. Is the cartridge on the Garrard good (most likely ceramic). Those are known to go bad sometimes or lack output on one channel.

thanks for this, the cart may be bad but that is not the issue at hand, the unit also has an AUX input, I can see audio on the 'scope from both sources make it's way through the switch

 

[KentTeffeteller]

Then trace through the succeeding stages, this is a reasonably simple amplifier.

 

[Mikefc]

which gets me to the OP, the transistor is where it stops

 

[Pvdg]

No info about the transistors but maybe this could help you a bit further: on eBay, search for Sams Photofact Folder Masterwork Model M2210 (or other model).I’ve seen some schematics, part lists, pictures: Maybe a start...

I hope you realise that, even after repair, audio performance will have its limits,also because of the cartridge.
Emotional, nostalgic value,ok, but nothing more.
Repaired some of these units (Wilson,Cosmo,SBR,BSR...).nice vintage look, that.s it..

 

[Mikefc]

understood. I'm fixing for a friend who owns a second-hand, vintage stereo shop. He believes the novelty of this is worth the repair ( within limits of course)

 

[century tek]

It's very rare that both channels would be out at the same time except from an over voltage event or spike so maybe try looking around the power supply area??

 

[Mikefc]

This is most likely germanium transistor equipped. Is the cartridge on the Garrard good (most likely ceramic). Those are known to go bad sometimes or lack output on one channel.

Kent

does .229 sound about right for the drop across a germanium ? If it is , this might measure ok and tell me it's PNP. There is a small dot on the can which I'm guessing is Base, with the drops in only one direction, I can play detective and figure these out.

 

[Mikefc]

It's very rare that both channels would be out at the same time except from an over voltage event or spike so maybe try looking around the power supply area??

good thought, I'll look further at that because I had put it aside when the TT motor worked and lamp was lit. But maybe I missed something.

 

[century tek]

Diodes, fuses, open resistors in the power supply would cause this. I think it's great that you know how to use a scope but I personally would ditch it for now and just use a basic volt/ohm meter and look for non-existent voltages.

Scopes are good for finding distortion, clipping, ringing, etc. when you want to dive into something deeper.

 

[Mikefc]

Diodes, fuses, open resistors in the power supply would cause this. I think it's great that you know how to use a scope but I personally would ditch it for now and just use a basic volt/ohm meter and look for non-existent voltages.

the scope is only the first test, put a 1kHz signal into AUX, trace it until it stops or distorts.... that brought me to these two components....

thank you for your input, I imagine we all have our tried and true methods when facing a circuit without schematic or component specs.

 

[century tek]

That thing is easy.

Like I said, if there is no output on either channel to begin with, in my experience, it has always been something to do with the power supply.

Now if it was already producing sound through the speakers but it was fuzzy and/or crackly or had hum, then the scope would be a good thing for tracing out the distortion, ringing, etc.