help with ampeg b100 vintage

[em123]

Hello, I recently acquired a vintage ampeg b100 for free. However when plugged in it is extremely distorted. I opened it up and didn't notice anything that was clearly wrong. However it did not have a fuse or place to place a fuse and on the second input the end of a frayed wire sat connect to nothing. I added a fuse and fuse connection and replaced the power supply however the amp is still distorted. Any help would be great.

[nosaj]

Hello, I recently acquired a vintage ampeg b100 for free. However when plugged in it is extremely distorted. I opened it up and didn't notice anything that was clearly wrong. However it did not have a fuse or place to place a fuse and on the second input the end of a frayed wire sat connect to nothing. I added a fuse and fuse connection and replaced the power supply however the amp is still distorted. Any help would be great.

There is a schematic on this link
http://music-electronics-forum.com/t38223-2/

[52 Bill]

Welcome to the place.

Please explain "replaced the power supply". If the amp was not modified, it should have had a fuse and fuse holder installed at the factory.

This is a fairly simple amp with a single sided power supply. Do you have a voltmeter available? Do you feel comfortable in working on an amp that is plugged in and powered on?

[em123]

It looks as if the amp was modified because the fuse and fuse holder were no where to be seen. I do not have a voltmeter available but will probably find one to use and I am comfortable working on a amp that is powered on and plugged in. let me know what I can do,

Thanks!

[Enzo]

What does "replaced the power supply" mean?

[em123]

I replaced the power cord and added a fuse and fuse holder, thats all the repairs I've done.


On the second input. The very end of a wire remains attached to the input, however it is not connected to anything else.

[The Dude]

WOH! Some observations: I would not use that type of fuseholder with open connections that can short to the chassis! Aside from that, it doesn't look like the connections to the holder are soldered very well, which is somewhat irrelevant. Get either a chassis mount holder and drill, or an inline holder that is sealed and connections can't touch the chassis. The way you have it is dangerous!

Next, power should connect (through the switch and fuseholder) to the transformer primary- hot and neutral to the 2 transformer wires. I can't tell from the pic. Is that what's going on? If so maybe the primary is open. Check it with a meter.

Whatever you do, please don't leave that fuseholder in there as is!

[em123]

Hi, I definitely will replace the fuse holder. I'm a noob at amp and electrical repair so I apologize for the he basic terminology.Currently the power is soldered to the switch and pilot light bottom tabs, where the previous power had been connected. Not sure if this is how it's supposed to be connected, just followed what was there.

Thanks

[The Dude]

Here's a schematic.

http://music-electronics-forum.com/attachments/32107d1419972083-b-100.jpg

With the unit unplugged and the power switch on, measure across the blades of the power cord plug. If everything is wired correctly, you will measure the resistance of the transformer primary. If you get an infinite reading, either the wiring is incorrect, there is a connection problem, power switch or fuse is bad, or the transformer primary is open.

Edit: Sorry, I got hung up on the power thing. I see you have power and the amp is distorted. We/I can move on.

[em123]

Haha no problem, any help is welcome. Just you get this straight the power should we wired through the fuse and to the switch?

[The Dude]

Do you have a way to test caps?. If not substitution or just replacing them would work. On something of this vintage, that would definitely be something to investigate. Particularly, the amp has a cap coupled output (C17). If that cap is bad, the output could be "messy". The schematic supplies you with voltage measurements. You should also check those to see if anything is out of whack with those.