Hello all, I need help with this one. I am repairing an AMEK psu that is for a Scorpion with Uptown Automation. It was thrown out because of a failure and I just had to scoop it up.
Transformer and rectifiers check out fine.
The failure was that two electrolytics exploded in such a way that the un-coiled metal film shorted to the case of the tip32 driver on one and to 0V on the other.
Attached is a schematic that is basically the same, except that both rails use the LM338/2955 and rails are rated for 10A. The caps that went supernova are C4, and one that isn't in the schematic- it is C10 on the pcb. It's across the rail at the output connector and bypassed with a small tantalum cap. Both lytics are 10uf 35v.
The unregulated rails are only ~28v so it wasn't over-voltage if the reg failed. Any ideas as to why those two caps would have blown? Thanks!
PS, is it possilbe for the TIP32 to measure a few ohms in any test lead configuration while in circuit as the pass driver?
Transformer and rectifiers check out fine.
The failure was that two electrolytics exploded in such a way that the un-coiled metal film shorted to the case of the tip32 driver on one and to 0V on the other.
Attached is a schematic that is basically the same, except that both rails use the LM338/2955 and rails are rated for 10A. The caps that went supernova are C4, and one that isn't in the schematic- it is C10 on the pcb. It's across the rail at the output connector and bypassed with a small tantalum cap. Both lytics are 10uf 35v.
The unregulated rails are only ~28v so it wasn't over-voltage if the reg failed. Any ideas as to why those two caps would have blown? Thanks!
PS, is it possilbe for the TIP32 to measure a few ohms in any test lead configuration while in circuit as the pass driver?
Attachments
Age is probably the primary contributor to electrolytic failure.
As these dry out with age and use, the ESR rises and increases the heat rise in the capacitor. This problem feeds on itself until the smoke is released.
My advice is to wholesale replace everything past the rectifier. The parts are relatively inexpensive(< $20 total).
Do you have the console as well?
As these dry out with age and use, the ESR rises and increases the heat rise in the capacitor. This problem feeds on itself until the smoke is released.
My advice is to wholesale replace everything past the rectifier. The parts are relatively inexpensive(< $20 total).
Do you have the console as well?
testlab, I will have to look at it which means digging through all the old consoles no one uses anymore. As mentioned in the first post it does have uptown automation, v1.0 I think.
We're getting a first national tour out the door tomorrow so it might be early next week. I'll will back to you.
We're getting a first national tour out the door tomorrow so it might be early next week. I'll will back to you.
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