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Marantz 2245 restoration... hit a snag and need some help, please!

P

pkcain

New Member
Hello AK'ers!

I'm new here. I don't have a lot of knowledge but I've restored a couple of HK330's, one wasn't working, and recapped a Tandberg TR1040 without issue.

I picked up a 2245 that the previous owner said "...had a quieter channel, so an output transistor was replaced and now it doesn't make any sound..." This was including a picture of the "new" transistor, which was marked S40449/510. I tried to cross reference this and didn't find a match, so I assumed it was the problem with the no sound issue.

When I got it home, it wouldn't trip the relay. I removed both output transistors from the RHS and tried again to find the LHS channel worked fine. I then switched the output transistors from the LHS to RHS and had music again. I then proceeded to order parts for a restoration of the power supply, preamp and power amp boards.

The PS board had been worked on previously with a bunch of cheap Ecaps replaced. I replaced them again with Elna SII caps, new transistors and a new relay (relay 'click' went from ~5 seconds to ~2seconds). Adjusted voltage and after replacing the RHS output caps, adjusting bias and DC offset, I ran the unit for a day. It sounded nice. I LIKE it! :-)

Now... I recapped the tone board (P400) and when I went to test afterwards, with the unit upside-down, I noticed the relay clicked almost immediately after I powered it up. When I turned on the speakers I get a loud hum on the RHS channel, irrespective of volume knob position. I tried without any inputs, and also without the pre/amp jumpers in the back. Same problem, hum when speakers are turned on. So, assuming it's an amp issue, I then checked DC offset and it's ~37v! Please keep in mind I haven't touched the amp boards, besides moving/replacing output transistors and adjusting of DC and bias. Everything adjusted fine and it ran all day without getting too warm or doing anything wrong.

So... now for the fun bit... any ideas on what could have happened (or did I do it?!) for hum and 37vdc? I don't think this is just a coincidence with something failing at the same time I'm working on another board.

Thanks for your time, and take care,
Peter
 
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You said the protection relay clicked in but your have 37volts of dc offset?? I would go back to the power supply and check all your voltages and compare to the schematic, maybe have a cap in backwards?
 
Aiden T said:
You said the protection relay clicked in but your have 37volts of dc offset?? I would go back to the power supply and check all your voltages and compare to the schematic, maybe have a cap in backwards?
Click to expand...
Hi,
Thanks for the response. The problem is only on one channel so I wasn't thinking PS issues., but I measured the PS output and it's dead-on 35vdc.

I wonder what would make the relay would click immediately upon pushing the power button, as opposed to the ~2 second delay as before (and ~with original relay and caps).
 
reasons for relay clicking instantly.
shorted relay driver transistor
open circuit timing capacitor .
short circuit .
 
Okay, I removed the RHS output transistors and now the relay clicks after a couple/few seconds as before. I tested the left channel and it sounds good. I also jumped the RHS pre-out to the LHS amp in to check the preamp board work and it also sounds fine.

*maybe this IS a coincidence! Unlikely, but maybe.

So, summary:
LHS amp works
RHS amp has output transistors removed due to hum.
PS board puts out 35vdc
Relay clicks as it should
Preamp, both channels plays through the LHS amp just fine.

Any suggestions on what to check as far as jumper voltages and such?

Thanks,
Peter
 
Last edited:
so when the RHS outputs are in the relay clicks immediately and you have 37 volts on the outputs? If there is that much dc the relay shouldn't engage at all.
 
FOund it! After reading a bunch of threads on this amazing site, and the previous question regarding working right side up, I figured something got moved/shifted/tweaked. I looked everything over and having not found anything I put the OT's back in after cleaning off any excess thermal compound, just in case, and it works! Relay clicks after 3 seconds, and it sounds balanced and nice! Now to just re-compound those OT's and move on.

Thanks for your help and time. Now to get those amp boards out for refurb....

Take care,
Peter
 
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