Hehe oh dear... Well I must say messing around with this amp has put me off owning anything made by Marantz. Cheapest quality components everywhere, really bad quality pcb with tracks that want to lift the second you touch them... Just horrible.
Anyway, I missed your post earlier so went ahead & removed every transistor bolted to the heatsinks... All test OK but two have been replaced in the past - Both 2SC4467 have been replaced with 2SD1047 in one channel which I had missed. Both 2SD1058 gave very high readings but the datasheet revealed they are darlingtons so that's why I guess.
I've got to travel away for a week so wont get another chance to do any more work on it until I return... I need to sort out a bulb tester, are the darlingtons you refer to the 2SD1058 ? And which relay to short ? the class a one on the PSU board or the output protection relays ? Or all ? 😀
Anyway, I missed your post earlier so went ahead & removed every transistor bolted to the heatsinks... All test OK but two have been replaced in the past - Both 2SC4467 have been replaced with 2SD1047 in one channel which I had missed. Both 2SD1058 gave very high readings but the datasheet revealed they are darlingtons so that's why I guess.
I've got to travel away for a week so wont get another chance to do any more work on it until I return... I need to sort out a bulb tester, are the darlingtons you refer to the 2SD1058 ? And which relay to short ? the class a one on the PSU board or the output protection relays ? Or all ? 😀
2SD1508 ? very blurry on the piccy. Relay to short would be the chattering one which I assumed to be the PSU one.
If the units already been worked on and has an unknown history then it could be an uphill job to sort it all out.
If the units already been worked on and has an unknown history then it could be an uphill job to sort it all out.
2SD1058 is the Vbe multiplier - bias controller etc. The output pairs are standard grade TO3P Sanken 23C4467/A1694 which are widely available as genuine parts. 2SD1047/B817 are everywhere on Ebay and possibly fakes - at least keep the outputs and drivers nominally complementary pairs.
Try this download for some clarity: Marantz PM-80 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine ,
Try this download for some clarity: Marantz PM-80 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine ,
Indeed. If I had known what I was taking on I would have declined but I'm too far in now... I can at least try to fix it [cant make it any worse!]
The chattering relay on the PSU board is related to the class a circuit [when you press the class a button it throws the relay as it should] but it only buzzes when not in class a mode.
Thanks Ian, I intend to replace the two 2SD1047 of unknown origin with 2SC4467. Just as well I removed them, the thermal compound has completely dried up & stuck to the mica washers... It flakes off like dry paint !
The chattering relay on the PSU board is related to the class a circuit [when you press the class a button it throws the relay as it should] but it only buzzes when not in class a mode.
Thanks Ian, I intend to replace the two 2SD1047 of unknown origin with 2SC4467. Just as well I removed them, the thermal compound has completely dried up & stuck to the mica washers... It flakes off like dry paint !
Just take it slowly and use the bulb tester. If you short the vbe multiplier out as I suggest then you should at least be able to get it all basically working with little trouble. Class A mode and a bulb tester probably won't work as the amp will be trying to draw more current than the bulb will allow.
You don't have any hunches then Mooly ? They've proven to be accurate thus far 😀
I'll do as you recommend once I get back next week. As ever, thanks for the help !
I'll do as you recommend once I get back next week. As ever, thanks for the help !
Hunches 😀
Outputs, drivers and all the low value resistors need checking around the output stages. With the vbe multiplier shorted out you should be able to work on the amp and take some basic measurements.
Impossible to second guess it really but a few key checks will reveal a lot. In particular check the emitter resistor packs on the outputs. All the evidence will be there in the form of resistance and voltage checks.
Outputs, drivers and all the low value resistors need checking around the output stages. With the vbe multiplier shorted out you should be able to work on the amp and take some basic measurements.
Impossible to second guess it really but a few key checks will reveal a lot. In particular check the emitter resistor packs on the outputs. All the evidence will be there in the form of resistance and voltage checks.
Hi all,
This is a very good amplifier, isn't it ? It claims to have a very low THD value considering other comercial amplifiers. That THD is real ?( i mean if we measure or simulate, the value will it be around 0.006% ? )
Thanks.
This is a very good amplifier, isn't it ? It claims to have a very low THD value considering other comercial amplifiers. That THD is real ?( i mean if we measure or simulate, the value will it be around 0.006% ? )
Thanks.
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Good day everybody!
I know this thread is old, but since I have the same amp with the same problem... two 1ohm resistors in the +57-57 rail
R859/R860 keep raising their value up to Megaohms preventing output relays to work.
I was wondering if you have sorted out what was the issue for this or any additional clue on what's going on.
Thanks for any help!
I know this thread is old, but since I have the same amp with the same problem... two 1ohm resistors in the +57-57 rail
R859/R860 keep raising their value up to Megaohms preventing output relays to work.
I was wondering if you have sorted out what was the issue for this or any additional clue on what's going on.
Thanks for any help!
In my PM80 Mkii the two 330µF were dead and caused this phenomenon.
I substituted all elcos on this board cause it's getting really hot. Most of the caps were dried out.
I substituted all elcos on this board cause it's getting really hot. Most of the caps were dried out.
I checked the capacitors in that board and seems all ok.Anyhow i replaced the two 330uf just to be sure but the problem is still there.After several powen ons/power offs the resistors open.Very frustrating.
I'm thinking to replace those 1ohm resistors with higher wattage resistors...
Instead of trying to find the root on this problem that is unexplained, maybe i will try to find a solution by lowering the current in those resistors?Maybe increazing the resistors a bit?
Any advice will be helpfull!
Thanks a lot!
I'm thinking to replace those 1ohm resistors with higher wattage resistors...
Instead of trying to find the root on this problem that is unexplained, maybe i will try to find a solution by lowering the current in those resistors?Maybe increazing the resistors a bit?
Any advice will be helpfull!
Thanks a lot!
Build/obtain a bulb/current limiter before proceeding to locate the problem - it'll save you spending lots of Euros replacing destroyed parts.
Here's a UK version of a bulb/current limiter.
And here's a deluxe version...
Good Luck!
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From the PM80 II schematic that I downloaded,
there are errors on page 7,
the J704 (supply power to output transistors) should be marked J705,
and J705 (supply power to driver transistors and input circuitry) should be marked J704,
*********
Something about the 1r resistors R859, R860,
1/4 w is a bit under wattage, it could be a safe issue to use 1/4w to protect,
it has to bear all the current in supplying power to the driver and input stages.
when current drawn increase, that resistors would suffer a lot from heat,
especially when components went defective or leaking or even shorted in the driver and input stages.
suggest to use 1r 1w to test the current flow and locate the faults,
may change back to 1r 1/4w when problems solved.
********
Please check also
page 7
R791, R792, 33r
R789, R790, 47r 1W
C715, C716, C719, C720, 220u/ 63v
best to change all of the above.
is much better to full check all the components,
transistors, resistors, diodes....bad joints, etc.
there are errors on page 7,
the J704 (supply power to output transistors) should be marked J705,
and J705 (supply power to driver transistors and input circuitry) should be marked J704,
*********
Something about the 1r resistors R859, R860,
1/4 w is a bit under wattage, it could be a safe issue to use 1/4w to protect,
it has to bear all the current in supplying power to the driver and input stages.
when current drawn increase, that resistors would suffer a lot from heat,
especially when components went defective or leaking or even shorted in the driver and input stages.
suggest to use 1r 1w to test the current flow and locate the faults,
may change back to 1r 1/4w when problems solved.
********
Please check also
page 7
R791, R792, 33r
R789, R790, 47r 1W
C715, C716, C719, C720, 220u/ 63v
best to change all of the above.
is much better to full check all the components,
transistors, resistors, diodes....bad joints, etc.