I've picked up a cosmetically nice Marantz PM-30, which is the same as the A-530 and Superscope BLA-530 and almost the same as the 1050.
Everything works (balance, treble, all inputs etc), but the output level is very low, turning the volume knob to about 3/4 provides a listenable signal, but lacking some punch.
It has never been touched inside (one owner apparently) and not used for 20 years. I've cleaned all the pots, even though they weren't scratchy at all.
I found a manual and started measuring, then decided to take out the filter caps to replace them, and now realise I can't do any more measurements until I get new caps.
The 6800uF caps measured at just under 5000uF, under spec but I think should have still been enough for the amp to function.
Given all functions work, I figure it has to be something common but I'm finding the schematic hard to follow. there are some voltages listed in the manual though, and they are out of spec in several parts. I can/will pull out the components to test, but wondering if this points to c804 having a problem? Red/yellow values are what I found in different manuals, black is what I measured.
Also lots of incorrect values around Q403 but that may be downstream from this issue and I guess is only one channel?
Everything works (balance, treble, all inputs etc), but the output level is very low, turning the volume knob to about 3/4 provides a listenable signal, but lacking some punch.
It has never been touched inside (one owner apparently) and not used for 20 years. I've cleaned all the pots, even though they weren't scratchy at all.
I found a manual and started measuring, then decided to take out the filter caps to replace them, and now realise I can't do any more measurements until I get new caps.
The 6800uF caps measured at just under 5000uF, under spec but I think should have still been enough for the amp to function.
Given all functions work, I figure it has to be something common but I'm finding the schematic hard to follow. there are some voltages listed in the manual though, and they are out of spec in several parts. I can/will pull out the components to test, but wondering if this points to c804 having a problem? Red/yellow values are what I found in different manuals, black is what I measured.
Also lots of incorrect values around Q403 but that may be downstream from this issue and I guess is only one channel?
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Just to be sure about the model - there seems to be more than on "30" from Marantz - could you post some photos?
The schematics and board layouts in the manual match exactly.
From research elsewhere I understand the Superscope version may have had cheaper capacitors, which I could believe as the PCB has multiple holes to suit different pitch on the connectors. This one has Elnas all the way through, three legs on the big ones.
From research elsewhere I understand the Superscope version may have had cheaper capacitors, which I could believe as the PCB has multiple holes to suit different pitch on the connectors. This one has Elnas all the way through, three legs on the big ones.
All sorted. R806 was meant to be 220 Ohms measured at 17.2k, not fully open but I swapped it out and all is good now. I put the filter caps back in for now, wondering if they really need to be changed since they are only 5% outside the original spec. (2 week wait for new ones).
Maybe should have picked it up just from the colour, I was wondering why this one resistor was pale green.
Maybe should have picked it up just from the colour, I was wondering why this one resistor was pale green.
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What "filter caps" are you referring to?
In general with gear of that age I usually replace all the smaller lytics and clean all switches.
No chance of any measurements?
The big ones 6800 uF in this case, spec is +/- 20% and these measure at 5100 uF which is - 25%. I thought about trying to reform them using the supply rails in the amp but they went back in circuit to test if changing the resistor worked.
I’m giving the amp to a relative as a gift and the occasion is soon, I will order new ones but I think I’ll do 10,000uF and retrofit them later if they don’t turn up in time.
I’m giving the amp to a relative as a gift and the occasion is soon, I will order new ones but I think I’ll do 10,000uF and retrofit them later if they don’t turn up in time.