This amp has some similar problems to the old notes I have on some of these Zed amps. I would say this amp is sort of similar in design feel to a Hifonics Generation X, but definitely not 100% the same.
No fets seem noticeable shorted. I checked all FETs and most of the drivers and all are checking -ok- while on the board. Still clamped to the heatsync for now.
This amp attempts to power on but falls directly into Protect. I tried my 5A supply and also through a 20A fused link and it still goes into protect after about 5 seconds.
PS is set to 13.65vDC, 5A max CC. OCP at 5A trips out so it may be trying to pull above 5A if it wasn't prevented from going into protect.
I've taken note of readings on the TL494 and the LM324 as follows. I think these may be OK but something is causing protect to engage.
TL494
1: 2.321
2: 2.935
3: 4.80
4: 0.224 (Initially 0.92)
5: 1.473
6: 3.462
7: 0.000
8: 13.65
9: 0.000 (Initially 2.12)
10: 0.000 (Initially 2.12)
11: 13.65
12: 13.65
13: 4.98 (Initially 5.00)
14: 4.98 (Initially 5.00)
15: 4.98 (Initially 5.00)
16: 10.96 (Initially 11.24)
LM324
1: 0.003 (Initially 12.00)
2: 12.56 (Counts from about 3v up to peak)
3: 6.75 (Initially 7.64)
4: 13.56
5: 8.99 (Initially 9.60)
6: 12.58 (Counts from about 2v up to peak)
7: 0.004 (Initially 12.20)
8: 0.003
9: 0.003
10: 0.000
11: 0.000
12: 12.14 (Initially 3.71)
13: 8.95 (Initially 9.50, then drops to 0.000, then up 8.95 across about 2 seconds each)
14: 11.72 (Initially 0.68)
Rail voltage actually pulses up to +-19.35vDC before going into protect.
I checked for any pulses of DC across speaker terminals. Channel 1 seems to have an issue, referencing non-bridged speaker terminals. The following figures are PULSED to speaker terminals before dropping back to 0vDC
CH1: -17.44vDC
CH2: +-0.5vDC
CH3: +-0.3vDC
CH4: +-0.4vDC
From here, I'm thinking I may want to try and have the amp come up without protection, so that I can measure things on Channel 1 and see what might be wrong or different.
Can I carefully lift a few pins of LM324/TL494 to force boot, or should I check something else first?
Thank you
No fets seem noticeable shorted. I checked all FETs and most of the drivers and all are checking -ok- while on the board. Still clamped to the heatsync for now.
This amp attempts to power on but falls directly into Protect. I tried my 5A supply and also through a 20A fused link and it still goes into protect after about 5 seconds.
PS is set to 13.65vDC, 5A max CC. OCP at 5A trips out so it may be trying to pull above 5A if it wasn't prevented from going into protect.
I've taken note of readings on the TL494 and the LM324 as follows. I think these may be OK but something is causing protect to engage.
TL494
1: 2.321
2: 2.935
3: 4.80
4: 0.224 (Initially 0.92)
5: 1.473
6: 3.462
7: 0.000
8: 13.65
9: 0.000 (Initially 2.12)
10: 0.000 (Initially 2.12)
11: 13.65
12: 13.65
13: 4.98 (Initially 5.00)
14: 4.98 (Initially 5.00)
15: 4.98 (Initially 5.00)
16: 10.96 (Initially 11.24)
LM324
1: 0.003 (Initially 12.00)
2: 12.56 (Counts from about 3v up to peak)
3: 6.75 (Initially 7.64)
4: 13.56
5: 8.99 (Initially 9.60)
6: 12.58 (Counts from about 2v up to peak)
7: 0.004 (Initially 12.20)
8: 0.003
9: 0.003
10: 0.000
11: 0.000
12: 12.14 (Initially 3.71)
13: 8.95 (Initially 9.50, then drops to 0.000, then up 8.95 across about 2 seconds each)
14: 11.72 (Initially 0.68)
Rail voltage actually pulses up to +-19.35vDC before going into protect.
I checked for any pulses of DC across speaker terminals. Channel 1 seems to have an issue, referencing non-bridged speaker terminals. The following figures are PULSED to speaker terminals before dropping back to 0vDC
CH1: -17.44vDC
CH2: +-0.5vDC
CH3: +-0.3vDC
CH4: +-0.4vDC
From here, I'm thinking I may want to try and have the amp come up without protection, so that I can measure things on Channel 1 and see what might be wrong or different.
Can I carefully lift a few pins of LM324/TL494 to force boot, or should I check something else first?
Thank you
Actually I think I might have just found the issue. I removed the large U-Clip on channel 1 to take a closer look at the 3 main transistors to measure what I thought was a short between 2nd legs of some of them. Once I remove the clip, the trace short I was seemingly finding vanished, and the amp was able to boot properly with ~0vDC across CH1 speaker terminals and +-26.4vDC rail.
I think there was something sandwiched between the back of one of the transistors and the sync. I didn't see anything really but maybe there was a metal spec causing a short through the kapton insulation. I blew it out with compressed air then cleaned the sync and back of the FEts with a bit of acetone on a Q-Tip, put some new sync compound on and clamped it back up. Now its staying booted OUT of protect.
With the clip re-installed I pressed VERY hard against the clip/transistors and its staying booted with 0vDC on CH1.
Awesome! I have to say this because I'm ecstatic about the situation. I paid $50 for this amp and am high right now that possibly don't have to buy anything to fix it!
Whoo-hoo I'm back in the game!
On to audio testing. I'm going to drive this thing to clipping as long as I can once I get the rest of my bench online and wired.
I think there was something sandwiched between the back of one of the transistors and the sync. I didn't see anything really but maybe there was a metal spec causing a short through the kapton insulation. I blew it out with compressed air then cleaned the sync and back of the FEts with a bit of acetone on a Q-Tip, put some new sync compound on and clamped it back up. Now its staying booted OUT of protect.
With the clip re-installed I pressed VERY hard against the clip/transistors and its staying booted with 0vDC on CH1.
Awesome! I have to say this because I'm ecstatic about the situation. I paid $50 for this amp and am high right now that possibly don't have to buy anything to fix it!
Whoo-hoo I'm back in the game!
On to audio testing. I'm going to drive this thing to clipping as long as I can once I get the rest of my bench online and wired.
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