Pioneer H-R99/100 distortion problem

[ChopperCharles]

My H-R99 8-track player has a heavily distorted right channel. I've cleaned it extensively, and that's not the problem. I've replaced all the caps on the amplifier board, and that's not the problem either.

At this point, I'm guessing the problem has got to be a bad transistor on the amplifier board. But how do I go about narrowing down which one it is? The service manual is completely useless for this kind of detailed repair.

Charles.

 

[laatsch55]

That's why oscilloscopes are used. Unless someone has dealt with the same problem before and knows which components go bad...

 

[62vauxhall]

I assume you've found found and cleaned the record/play selector slide switch on the PC board?

There are 18 transistors on the amplifier board and the parts list identifies what their numbers are. They will most likely all be obsolete by now but you can find substitutes and replace all of them.

I shelved an HR-100 myself and will do a wholesale transistor change one of these days - it developed low playback output on one channel literally between tapes. Since then I've been using an Akai CR-81D so no great rush.

View attachment hfe_pioneer_h-r99_service_en pictorial (2).pdf

 

[ChopperCharles]

Great, so other than "randomly replace parts until it's better," I'm SOL. Sucks that I paid good money for this and it doesn't work.

Charles.

 

[62vauxhall]

There's this web page www.vetco.net/blog/?p=184 which is a method to check transistors with a digital multimeter. I've used it myself several times on in circuit transistors. Not as telling as with an extracted transistor but it will show a fault. It's a bit of a chore but you should be able to pinpoint a bad transistor if that's what you have. My thinking was that transistors are cheap so why not replace them all.

In addition to the record/play slider switch, there is also the program selector switch. Have you cleaned it?

 

[62vauxhall]

There's this we page www.vetco.net/blog/?p=184 which is a method to check transistors with a digital multimeter. I've used it myself several times on in circuit transistors. Not as telling as with an extracted transistor but it will show a fault. It's a bit of a chore but you should be able to pinpoint a bad transistor if that's what you have. My thinking was that transistors are cheap so why not replace them all.

In addition to the record/play slider switch, there is also the program selector switch. Have you cleaned it?

 

[laatsch55]

Gary, checking for shorts and opens is just part of the story. After you determine it's neither shorted or open the next step is determining whether or not it has gain. That has driven me crazy at times, ie the bias circuit on a PL amp. The ol 2N3403's can test good and still have no gain, and that does not let the bias circuit do it's thing...can be hair pulling stuff. I bought a cheap Sencore HFE tester....worth it's weight in gold...