Leokarma
Well-Known Member
This is going epic! If you give up send it to me and I'll take a crack at it just for the academic aspect of it.
sure. I would have let it go but now it's a challenge.
2275 relay not engaging - Problem with left Amp section
- Thread starter Leokarma
- Start date
sure. I would have let it go but now it's a challenge.
Leokarma
Well-Known Member
R735 was smoking but I replaced it and is fine now.
Leokarma
Well-Known Member
I removed H713 and checked it again and it was ok. I removed H711 and given below are H713 voltages without H711,
e -45.4 (minus)
c + 46.2
b -46.1 (minus)
Regards
Leokarma
Well-Known Member
yes R727 is OK
Leokarma
Well-Known Member
Well this was one of the first few components that I removed and since I had taken it out to test, I thought I might as well replace it with new. I had a new resistor with me but it was the cheap Chinese resistor (same value, same watt). I guess Chinese resistor was not up-to-mark and failed. I immediately reinstalled the original resistor and it was ok. I checked the temperature with laser thermometer and it's not heating up anymore.
petehall347
the brandy coffee man
was the grounding checked ?
best also check h709 .
i can only guess at things as there are more than 1 thing that can be happening here .
best also check h709 .
i can only guess at things as there are more than 1 thing that can be happening here .
Leokarma
Well-Known Member
I had checked H709 earlier and it was ok. How should I check grounding ?
petehall347
the brandy coffee man
j709 j710 each have grounds . and have to be connected well .
shown as a thick black line on the schematic . they should connect to the chassis ground .
shown as a thick black line on the schematic . they should connect to the chassis ground .
Leokarma
Well-Known Member
Last thing that I think I would like try is change few suspected transistors before 'calling it a off'. After that I would prefer to replace the entire board if I can find one in working condition. As it is, due to repeated solder and de-solder the track of H711 and H713 are in bad shape. Do you guys think it worth replacing few transistors and check or just waste of time ? I was thinking H714, H713, H709 and H712. H711 was replaced twice so I'll leave it as it. Should I include any other component ?
Leokarma
Well-Known Member
I checked this using continuity tester and ground seems well connected
petehall347
the brandy coffee man
ok .
if you could manage to post a copy of the schematic for your board with the voltages you measure next to the marked ones .
some people do this easily .i know i cant .
i do think it would be a good idea to check every resistor and transistor whilst still in the board with power off . see if anything stands out .
i do seem to think this is going to end up being the differentials not playing .
if you could manage to post a copy of the schematic for your board with the voltages you measure next to the marked ones .
some people do this easily .i know i cant .
i do think it would be a good idea to check every resistor and transistor whilst still in the board with power off . see if anything stands out .
i do seem to think this is going to end up being the differentials not playing .
Leokarma
Well-Known Member
ok .
if you could manage to post a copy of the schematic for your board with the voltages you measure next to the marked ones .
some people do this easily .i know i cant .
please see attached....
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petehall347
the brandy coffee man
h715 h716 15v zeners .
c704 c703 both in backwards .
r716
r717
look at those zeners first ..maybe mistakenly swapped for regular diodes or incorrect voltages .
there should be 15v accross each of those zeners .
r716
r717
should have approx 30v across each .
c704 c703 both in backwards .
r716
r717
look at those zeners first ..maybe mistakenly swapped for regular diodes or incorrect voltages .
there should be 15v accross each of those zeners .
r716
r717
should have approx 30v across each .
Leokarma
Well-Known Member
C704 and C703 are installed correctly as per -/+ on PCB and also other working Chanel.
Please see below voltage around R716, R717 and H715, H716
Across R716 and R717 it should be 30 VDC but it's 38 and 40.6
Similarly across H715 and H716 it should be 15V but its 8.6 and 5.9.
I did diode check H715 and H716 earlier but did not check the specification / correctness of voltage etc. If required I can replace these with equivalent diode. These are WZ-150 and I think the replacement is BZX85B15 which I have in my stock.
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petehall347
the brandy coffee man
yes they should regulate the voltages to 15v +-
i just noticed h701 base being at 6.5v .. it really cant be and should be close to 0v .
h701 may have a problem .
i just noticed h701 base being at 6.5v .. it really cant be and should be close to 0v .
h701 may have a problem .
Leokarma
Well-Known Member
Yes sorry you are right. Base of H701 is in fact close to zero. I have revised the images. Not sure how i made mistake. I generally measure 3 times before putting it down on paper.
Do you still think H701 could be the problem or it's ok ?
petehall347
the brandy coffee man
base of h702 appears high because of the high voltage further on .
if you turn r741 it should change that voltage .
if you turn r741 it should change that voltage .
Leokarma
Well-Known Member
Turning R741 has no affect on H702 base voltage. It's constant @ +7.2 VDC
