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Man O War DX Problems

Started by DLW, April 18, 2020, 09:41:35 PM

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DLW

I'm struggling to troubleshoot my MOW DX build. It passes sound, but there is no modulation/delay. The rate and bypass LEDs work, and the LDR LED flashes. Based on the voltages I suspect there is something weird going on with Q6 or Q7 which then throws off the voltages for the clock and BDD. I replaced Q7, R51, and R53 to no avail. I also visually verified that R50 and R52 are correct. Anybody know why the collector voltages would be so low? Am I right in assuming this would cause the clock and BDD to not function properly?

Voltages:
Q1 (2N3904; CBE) - 12.4, 4.2, 3.76
Q2 (2N3904; CBE) - 12.4, 2.85, 2.25
Q3 (2N3904; CBE) - 12.4, 7.4, 6.8
Q4 (2N3904; CBE) - 12.4, 7, 6.5
Q5 (2N5088; CBE) - 0.45, 0.45, 0
Q6 (2N5088; CBE) - 2.2, 0.5, 0
Q7 (2N5087; CBE) - 2.15, 12.2, 12.2

IC1 - 6.12, 6.13, 6.13, 0, 6.12, 6.12, 6.12, 12.4
IC2 - 1, 1.8, 1.8, 0, 1.87, 1.87, 2.9, 1.87, 1.87, 4.3, 4.3, 1.87, 12.4, 1.87, 1.87, 0.9
IC3 - 12.4, 0, 6.9, 5.8, 0, 11.79, 6.23, 0.8
IC4 - 11.8, 0, 0, 11.8, 11.75, 2.8, 3.7, 0.8
IC5 - 12.4, 0, 5.3, 6.3, 0, 11.7, 5.25, 0.8
IC6 - 11.7, 0, 0, 11.7, 10.6, 2.6, 2.1, 0.8
IC7 - ?, ?, ?, 0, ?, ?, ?, 12.2

Pictures:
Solder

Component


Scruffie

Well you're right your clocks aren't working, which yeah does mean no delay.

So you know the LFO works, audio path we'll assume is fine and you're right, the problem area is Q6 & 7 and IC4 & 6.

Where did you source the MN3101 from? Was it reliable? It might be worth popping them both out and seeing what happens to Q7's voltage and also if you have a spare 2N5087 popping it in.
Works at Lectric-FX

DLW

Thanks for the reply, Scruffie.

The MN3101 was from UTSource, if memory serves. I've actually pretty good luck with chips from them, but I still checked all the clocks in a functional circuit. They work. I also swapped them for others in the MOW and the voltages are about the same as the old ones. I swapped Q7 for a new 2N5087. No difference. When I removed the clocks and measure Q7, the collector drops off to ~ 0V. The base and emitter stay at ~12V.

Scruffie

Okay, rules that out then, so I'm looking at your photos, while the soldering is good, Q6's collector pin does look a little off, could be the lighting though.
Works at Lectric-FX

DLW

I think the solder joints on Q6 are good. Here are better? pictures. I also reflowed the joint, but alas, it did not help :(