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Issue with SA-7800

ah ok my mistake .. its the way i looked at d30 at the bottom . i never noticed the second one up as thought the 0v was both ends ..
 
You will probably find that investing in a decent meter will help a lot. Not just in terms of features but also testing accuracy .

I found an audible continuity test was really useful as was built-in transistor testing.

I'm following this thread with interest so good luck in getting your 7800 going - I just sold mine....
 
Okay we're back in business with a new Multi-Meter... nothing special but will do the job.

DC Readings:

D30 anode: -64.7
D30 cathode: -0.00

D27 anode: 0.00
D27 cathode: 63.2

D29 anode: -64.6
D29 Cathode: 0.00

D28 anode: 0.00
D28 Cathode: 63.2
 
Markoneswift said:
You will probably find that investing in a decent meter will help a lot. Not just in terms of features but also testing accuracy .

I found an audible continuity test was really useful as was built-in transistor testing.

I'm following this thread with interest so good luck in getting your 7800 going - I just sold mine....
Click to expand...
Awesome to have you part of the thread Mark!!

Here is the new MM... i can't tell if it has a built-in transistor testing, but it does BEEP when there is continuity
newmm.jpg
, so that's cool :)
 
now find those U shaped heat sinks fastened to 2 transistors and see what DC voltages are there . voltage should be on the heat sinks so this shouldn't be difficult
 
So we have +63V on Q34 collector and -63V on Q35 collector. Check DC voltages on test point 15 and test point 21
 
okay I think I "may" have found the 2 transistors with the heatsinks on them... are they tan shaped with one of them between the 4 diodes? Here is a picture with them circled...

transistors.jpg
 
Ryan Walton said:
okay I think I "may" have found the 2 transistors with the heatsinks on them... are they tan shaped with one of them between the 4 diodes? Here is a picture with them circled...

transistors.jpg
Click to expand...
right at the bottom of this picture .. see the 3 legs on the transistors ?
 
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