Mysteriously healed bedrock BC50

[bard2dbone]

I have a Bedrock BC50. When I got it, it was the perfect amp: 50 Watts, one channel sounded like an old tweed Fender, the other sounded like an AC30. Since those were my two favorite sounds right then, I was pretty thrilled.

But Bedrock smacks these things with insanely huge biasing voltages. So the tubes run REALLY hot and actually put out more wattage than the circuit should be expected to. The downside is that leads to much shorter tube life.

The last time I had it re-tubed, it soon developed a weird new hum. It was somewhere in the switching circuit, obviously because it hummed on one channel but not the other with the footswitch plugged in, but swapped to the other channel and no longer the first one with the footswitch unplugged. In summary: ugly hum, one channel at a time, which one depends on the footswitch being attached.

So I quit using it. It sat for a long time (most of this year) without even being powered up. I used my Vox Tonelab for practicing. I used an old Crate that I kept for my kids to use f they took up guitar, I played un-amlified a LOT.

Then this week I decided to take it to a new shop someone mentioned, but before I left I decided to fire it up and see how it sounds now.

The noise was gone. The amp doesn't have the tone I bought it for anymore. But it really hasn't sounded like that since the shop visit where the guy had it for almost a month before he admitted he couldn't figure out what to do with it(No schematics available) and "Oh by the way, I swapped out your power tubes."

So I don't really have my old amp back. But now I at least have a working tube amp. Maybe I can learn to like this somewhat harsher, more brittle sound. Maybe I can find an amp tech who knows what to do with Bedrock products.

[Tbone135]

Well, we are in the season of miracles. I hear that the Bedrocks aren't difficult to work on, but I've had no problems with mine so I don't know.

[bard2dbone]

Which one is yours?

And at least one guy found mine really hard to work on. It's never sounded like it used to again.

[Tbone135]

It says "600" on it and it's 4 EL84 with a 1x12 speaker, I don't know the model number of it. I used it for church this morning and it sounded great; very Marshall-plexi-ish to me.

[bard2dbone]

A 50 Watt (Yes, 50 Watts from four EL84's, That's why I commented about insane biasing vooltages and shortened tube life.) 1X 12 in the 600 series would be a model 651.

Go look at this page and see if yours is there. http://bedrock27.tripod.com/bedrockamp/id9.html Mine is the kind of Vox-looking blonde one in one of the pics below the one that I think is like yours. The 651 in the pic is in tweed. But most of them that I saw back in the day were plain black tolex. One guy I knew had one in snakeskin and one in leopard. He was kind of odd.

Where are you? If your tech had no probs working on yours, he could probably do fine with mine.

[Mastervolume]

if a tech needs a schematic to work on a bedrock you have the wrong guy.

[redfro]

Originally Posted by bard2dbone

A 50 Watt (Yes, 50 Watts from four EL84's, That's why I commented about insane biasing vooltages and shortened tube life.) 1X 12 in the 600 series would be a model 651.

Go look at this page and see if yours is there. http://bedrock27.tripod.com/bedrockamp/id9.html Mine is the kind of Vox-looking blonde one in one of the pics below the one that I think is like yours. The 651 in the pic is in tweed. But most of them that I saw back in the day were plain black tolex. One guy I knew had one in snakeskin and one in leopard. He was kind of odd.

Where are you? If your tech had no probs working on yours, he could probably do fine with mine.

I have the exact BC-50 in the pic, and I have had some problems before. My amp tech (http://www.myspace.com/dabeckcustomamps) didn't have any problems working on it without scems. He just redressed some of the leads and iso'ed some stuff to clean it up. Same sound, less noise.

[bard2dbone]

Originally Posted by Mastervolume

if a tech needs a schematic to work on a bedrock you have the wrong guy.

Originally Posted by redfro

I have the exact BC-50 in the pic, and I have had some problems before. My amp tech (http://www.myspace.com/dabeckcustomamps) didn't have any problems working on it without scems. He just redressed some of the leads and iso'ed some stuff to clean it up. Same sound, less noise.

I'm guessing that normal issues wouldn't have been hard for him. There are only so many ways to make a basic amplifier circuit.

But if you get something really odd happening outside the audio path that is effecting things in the audio path, then you really need a schematic.

I was an electronic tech back in the day, but I never worked on amplifiers. All my experience was on radars and satellite communication gear. It's a pretty different world.

[Mastervolume]

Originally Posted by bard2dbone

I'm guessing that normal issues wouldn't have been hard for him. There are only so many ways to make a basic amplifier circuit.

But if you get something really odd happening outside the audio path that is effecting things in the audio path, then you really need a schematic.

I was an electronic tech back in the day, but I never worked on amplifiers. All my experience was on radars and satellite communication gear. It's a pretty different world.

I am an EE who worked on GPS satellite development back in the 80's for Rockwell.

When I went to school they never even mentioned tubes.

If we were talking about opening up a boogie with a million switches and circuit boards or hell even a solid state fender from the 80's then I would say sure a schematic will make things much faster and easier.

But...... a vox/marhsall/fender style circuit that is point to point (like the bedrock) should be a no brainer. A good tech would have only seen similar topography many times before he ever looked at the bedrock.

[bard2dbone]

Well, like I said, the audio signal path probably looks basically like a million other amps. But if the problem is in the switching circuit and it's causing an apparent loading issue somewhere in the audio signal path, that's just weird. I'd want a schematic before I got too in-depth into something that odd.

This wasn't a normal problem. The guy I took it to had done fine with any number of normal problems over the years and surely would have done so again. This was a tip-your-head-over-a-little-bit-and-make-that-confused-face problem.

[rabidears]

I love that amp but it has been a bit of a shop queen. Does not sound like the amp that i bought. But,,,,I will never sell it., I know someone can get it back to what it was. Been worked on by 2 techs and both had issues w/ the layout but loved it tonaly.I've had to replace 3 clean volume pots redo the 8ohm speaker out blew the original speakers the list goes on. Thanks for the link. He has a zinky, he built my first real amp back in the 80's
my first post here thanks
chris