Very good point; I should have stated clearly that the example was meant to illustrate that the 'continuity' measurement can be misleading and that one should see if the resistance value is reasonable for the particular situation.
Thank you for clarifying.
Cheers,
Dennis
Thank you for clarifying.
Cheers,
Dennis
Thank all of you for your thoughtful responses.
I dressed/twisted the wires. Maybe easier to see what's what. New picture; shows fuse holders. There are no shorts to chassis ground between L and N. Tested the front panel switch; it was ok. The front panel switch was added long before the current problem and has been trouble-free. Continuity checker beeps between .5 and .7 ohms. I measured the cl60s. They ranged between 7.9 and 8.2 (measured in place).
Should I try powering up yet or is there something else you see or that I should double check? When I power up I'll first disconnect the transformer secondaries per previous suggestions and if that goes well hook up the capacitor banks and then the amp boards themselves. With the dual fuses I can do one side at a time. But I'll wait to hear from you all.
I dressed/twisted the wires. Maybe easier to see what's what. New picture; shows fuse holders. There are no shorts to chassis ground between L and N. Tested the front panel switch; it was ok. The front panel switch was added long before the current problem and has been trouble-free. Continuity checker beeps between .5 and .7 ohms. I measured the cl60s. They ranged between 7.9 and 8.2 (measured in place).
Should I try powering up yet or is there something else you see or that I should double check? When I power up I'll first disconnect the transformer secondaries per previous suggestions and if that goes well hook up the capacitor banks and then the amp boards themselves. With the dual fuses I can do one side at a time. But I'll wait to hear from you all.
Are you sure about that switch, it has 7 - 7.5 amps flowing through it with those two donuts. Can you disconnect the leads from the switch and then jumper them together (make sure the amp is NOT plugged in until the leads are jumped), then just plug the amp in, see if it blows the fuse. This way the switch is no longer suspect.
What type of on-off switch is used for the two runs of AC?
It needs to be a double pole switch, with one pole for each AC run since the switch is after the fuses.
A single pole switch can be used if it is located between the IEC and fuses.
It needs to be a double pole switch, with one pole for each AC run since the switch is after the fuses.
A single pole switch can be used if it is located between the IEC and fuses.
Is there a model number for that switch? Many of those don't have particular high current ratings.
The switch is rated 5 amps/250 volts. Amazon:
Ulincos® Latching Push Button Switch U19C2 1NO1NC SPDT ON/Off Black Metal Shell with Blue LED Ring Suitable for 19mm 3/4" Mounting Hole (Blue)
As I posted earlier, I have jumpered around both switches and fuse still blew. Judging from your posts, however, it sounds like the switch should be rated 10 amps.
Looking at your picture, I cannot tell whether the switch is connected to the AC. If it is, disconnect it from the AC.
It is probably best to start at the beginning:
1. Disconnect both left and right transformer secondaries from the bridge rectifiers.
2. Disconnect the left channel fuse. Connect AC Volt meter to the right transformer secondaries and turn on power and check for proper secondary AC voltage.
3. Reverse channels and check the left transformer secondaries.
4. If the transformers check out, connect the bridge rectifiers to the transfsormers, disconnect the bridge rectifiers from the PS boards.
5. Again one channel at a time, check the bridge rectifier DC voltages.
6. If that checks out, connect the PS boards, with the amplifier boards not connected.
7. Again one channel at a time, check the V+ and V- DC voltages.
It is probably best to start at the beginning:
1. Disconnect both left and right transformer secondaries from the bridge rectifiers.
2. Disconnect the left channel fuse. Connect AC Volt meter to the right transformer secondaries and turn on power and check for proper secondary AC voltage.
3. Reverse channels and check the left transformer secondaries.
4. If the transformers check out, connect the bridge rectifiers to the transfsormers, disconnect the bridge rectifiers from the PS boards.
5. Again one channel at a time, check the bridge rectifier DC voltages.
6. If that checks out, connect the PS boards, with the amplifier boards not connected.
7. Again one channel at a time, check the V+ and V- DC voltages.
Thanks everyone for all of your ideas and support. I've powered it back up one section at a time. IT'S WORKING!! It's been on for 20 minutes and it seems to be back to its old self. Haven't hooked it back into the system yet-- that's tomorrow. I implemented most of your suggestions and the amp is better for it. When all is said and done I think switching to slow blow fuses is what did it.
Hey, that was me! I learned something from that which will forever be in my knowledge base.
A great way to learn!
Ya slow blow fuses ALWAYS on these class A amps. I think that detail is even specified on the First Watt power supply schematics if I'm not mistaken. The inrush current is nasty at switch-on.