2040 hot chassis and other problems

Just tested TR911 out of circuit and it's good.

Yes, one of the trasistors in the protection circuit is toast, had a marantz 2270 do that to me.

None of the transistors in the protection circuit are shorted. Could an open-circuit fault cause the problem?
 
Just tr911 or did you pull all in the protection circuit and test? To properly test they may need to come out.
 
I only pulled the one transistor. I assumed that the offending part would be shorted, and none of them were.

I might check the power indicator circuit too... It seems pretty closely tied in with the protector...
 
I would suspect TR910 and/or 911. Check your voltages around those two transistors and fill in the blanks..
TR910
E
C
B
TR911
E
C
B
 
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I may have found the culprit... When the dial face lamp connectors shorted, it took out D912. D910 (1S1555) is in series with it so I desoldered and tested it...it measured a couple ohms both ways so it's definitely toast.

Unfortunately I don't have an exact substitute on-hand but I found some 1N4154's in my stash. Would it work in this application?

Looking at the two datasheets the specifications appear similar:

1S1555 datasheet

1N4154 datasheet
 
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I may have found the culprit... When the dial face lamp connectors shorted, it took out D912. D910 (1S1555) is in series with it so I desoldered and tested it...it measured a couple ohms both ways so it's definitely toast.

Unfortunately I don't have an exact substitute on-hand but I found some 1N4154's in my stash. Would it work in this application?

Looking at the two datasheets the specifications appear similar:

1S1555 datasheet

1N4154 datasheet

looks ok to me .
 
I may have found the culprit... When the dial face lamp connectors shorted, it took out D912. D910 (1S1555) is in series with it so I desoldered and tested it...it measured a couple ohms both ways so it's definitely toast.

Unfortunately I don't have an exact substitute on-hand but I found some 1N4154's in my stash. Would it work in this application?

Looking at the two datasheets the specifications appear similar:

1S1555 datasheet

1N4154 datasheet

The N4154 is a little lower Prv than the S1555. D910 and D912 have 24-26vdc so they could still be used. (1N4154's prv = 35vdc)
Personally I would use a 1N4148 at 100 volt prv. I probably keep at least 500 in stock.
 
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