Marantz 2238B - Service Notes

[@hugeshows]

Correction: The hot transistor I added a heatsink to was Q750 not Q751. It is a 2SC1885 according to the service manual.

[@tuantrd]

Thanks

[@Jordanmilo]

I'm so glad to hear someone finally tell the truth about the construction of the 2238B. I've had mine since new in 1978 (still have the box, packing materials, owner's manual, sales receipt). The right channel went silent decades ago for all inputs. I've paid for repairs two or three times--those repairs last for a while and then the channel goes silent again. Now the Marantz functions only as a switched outlet for a Bluetooth converter for a modern Sherwood receiver. I can't put the Marantz back in the box, though, for sentimental reasons and because it looks so damn cool.

[@CP-qe2ym]

Great video, I'm getting a parts list together to recap my 2238B. So let me get this straight, you fabricated a small board and fitted four 100ohm 1 watt resistors in series rather than order and fit a 100ohm 4watt resistor? And I can't quite hear what you say at 4:22 but it seems important.

[@hugeshows]

Yes, that's what I did because those were the resistors I had on hand. Obviously a more elegant solution can be had if you're ordering parts in advance, although the board does get the heat away from the diode... there was no spot on the original board for both. I said I used a new 1N4007 diode in place of the old glass one.

[@CP-qe2ym]

@@hugeshows thank you for the clarification and quick response. I will follow your advice and replace the resistor with a 4watt and fit the diode. Cheers,

[@hugeshows]

4w is probably overkill, but it does run cool...

[@wedoshotz6645]

Q750 is listed as a 2SC1885, which should be a TO-92(L) case, however the one I'm working on (as was yours) is a TO-126 which I can't ID because the heat has dulled the case so much. I'm going to try to find a more robust replacement since I'm still in the middle of repairing this. Marantz receivers are not the most repair-friendly.

[@cheaprubbergarage6015]

Great video, I have one I'm trying t0 troubleshoot and it was working and I lost power to the lights and tuner signal meters at the same time I don't see anything burnt, where should I start at with this ?

[@hugeshows]

Get a schematic and start measuring all the rail voltages. You'll probably find one is missing. Be careful, amplifiers can kill you.

[@cheaprubbergarage6015]

@hugeshows thank you I'll be careful, I'm familiar with electronics, I have 20v on j709 and j710

[@cheaprubbergarage6015]

Also q750 is getting very hot on mine as well

[@pradeepramgobin4904]

Can u help me fix my marantz 2238b please