Guru
Joined: 12/08/2011
Location: AustraliaPosts: 357
| Posted: 01:14am 18 Jan 2023 |
i All
I started by taking the Q! & Q2 out on both boards and measuring
all voltage points.
Between the two boards there was an average difference of 50mV on various points
so I think that is probably fine.
Then replaced all the electro caps on the good board and tested again.
Made very little difference.
I started testing the Transistors last night but decided instead to order new ones
and test while waiting for delivery.
The Transistors are Q1 = MJE6041 & Q2 = MJE6044 (suppose to be 2N604* compatible)
The best match and delivery was
STM TIP102 x 5 for $10.90 on eBay (Sydney stock)
STM TIP107 x 4 for $9.00
The only difference between them & original is B - E res = 5k + 150 ohm
where the MJE6041 is 8k + 120 ohm.
Don't think it will make any difference.
The good board had a significant resistance difference between the NPN & PNP but
are suppose to be identical according to the spec sheet.
So, perhaps one of them may be damaged as well.
Before the transistors arrive, I will quantify things and test with 1vpp signal again.Didn't want to nominate a faulty Q1 or Q2 until proper test was done.
Also with both boards having the same transistors will make the final test more meaningful.
Sofar so good.