Hi
I recently picked up a Marantz PM-80, which seemed in pretty good condition - no bulging caps and not too dusty on the inside.
There was no turntable installed at the seller, so it wan't till after bringing it home and hooking it up I could hear there was a really bad hum when selecting phono (all other inputs were fine).
I have taken it apart sufficiently enough to see that there was one of the pins off the phono connector that had delaminated the lead off the pcb. I repaired it by just adding a small piece of wire from the offending pin to the next solderpoint on the track. (after resoldering the phono RCA connector to the pcb, of course).
Easy - problem fixed - no more hum. No more sound what so ever, actually 🙁
Absolutely nothing escapes from the PM-80 now, from any input channel.
Inspired by WaveyDipole's thread Marantz PM80 dead within 10 minutes I took some some voltages off the STK3102-IV as well as the trannys that are cooled by the big heat sinks, and there are definately som values that are wrong.
The protection relay is clicking in, but I cannot hear or feel the 2 speaker relays (LN01/LN02) do anything.
I've attached a spreadsheet with my readings, and I'd appreciate if some of you can suggest where to go from here.
I recently picked up a Marantz PM-80, which seemed in pretty good condition - no bulging caps and not too dusty on the inside.
There was no turntable installed at the seller, so it wan't till after bringing it home and hooking it up I could hear there was a really bad hum when selecting phono (all other inputs were fine).
I have taken it apart sufficiently enough to see that there was one of the pins off the phono connector that had delaminated the lead off the pcb. I repaired it by just adding a small piece of wire from the offending pin to the next solderpoint on the track. (after resoldering the phono RCA connector to the pcb, of course).
Easy - problem fixed - no more hum. No more sound what so ever, actually 🙁
Absolutely nothing escapes from the PM-80 now, from any input channel.
Inspired by WaveyDipole's thread Marantz PM80 dead within 10 minutes I took some some voltages off the STK3102-IV as well as the trannys that are cooled by the big heat sinks, and there are definately som values that are wrong.
The protection relay is clicking in, but I cannot hear or feel the 2 speaker relays (LN01/LN02) do anything.
I've attached a spreadsheet with my readings, and I'd appreciate if some of you can suggest where to go from here.
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You started with a working amplifier and now it isn't so logically, there is a mistake in your repair there. Recheck your work very carefully with a magnifier and a good light. Then, as routine checks, make sure the power supplies to the board (+/- 15V, 24V) are correct and the voltages on the IC, Q405 are approximately correct.
As this is likely now a DC offset problem ( test the power amp output(s) before the relay), perhaps you removed a PCB and perhaps haven't noticed a small ground connection or other?
Take care with testing when using plain meter probes - use IC clips or leads etc. to prevent slipping as you watch the meter.
As this is likely now a DC offset problem ( test the power amp output(s) before the relay), perhaps you removed a PCB and perhaps haven't noticed a small ground connection or other?
Take care with testing when using plain meter probes - use IC clips or leads etc. to prevent slipping as you watch the meter.
Pm 80 suffers only from poor soldering down under the main amp ...other than that nothing else
May be a few capacitors but that is highly unlikely for this amp even at this age .
I expect that you have the amplifier open as we speak yes ?
Far away bell rings saying that there is chance that some parts take ground from the cover ( if memory serves well ) and if there is screw missing ground is not there so front stages are out of balance so offset in the outputs and relays do not click .
Please check that ...this is Philips rubbish ideas ...
If this works consider a heatsink for the STK it will help keeping it alive longer
Kind regards
Sakis
May be a few capacitors but that is highly unlikely for this amp even at this age .
I expect that you have the amplifier open as we speak yes ?
Far away bell rings saying that there is chance that some parts take ground from the cover ( if memory serves well ) and if there is screw missing ground is not there so front stages are out of balance so offset in the outputs and relays do not click .
Please check that ...this is Philips rubbish ideas ...
If this works consider a heatsink for the STK it will help keeping it alive longer
Kind regards
Sakis
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