Help! Roland Bolt Hybrid Combo

BBB2005

HI Guys, 

Need some advice please.

I have a 30w Roland Bolt from early 80's with a lovely clean sound and crap high output channel. The clean channel has been all I have used and with a TC Electronics G major was excellent for my purposes. About 18 months ago the TC died and I stopped using the Bolt. About 6 months ago I gave it a blast and it had lost a great deal of volume (it was never loud) I changed the original RCA tubes for EH but it doesnt just break about 5 on the dial it sounds bloody horrible.

So, Is it shagged? could I use a pre amp directly to line in and get back my clean channel? Is the original Roland speaker knackered or should I just get another amp and can this?

The Roland Bolt is hybrid with the pre amp coming off a solid state circuit, hence why I thought a pre amp may assist.

Any views/comments and advice is appreciated.

Cheers

Steve 

ICBM

Does the speaker plug in on a cable, or is it hardwired? (Can't remember but possibly hardwired.) If it plugs in on a cable try running it through another cab, that will confirm or eliminate the speaker as the cause. If you don't have access to a cab you're probably best to take it to a tech for a check anyway.

If it's sat unused for some time, was working before, and now isn't, chances are an electrolytic cap has failed - they decay when not used, when they get old. It's probably worth getting it fixed, although I know they aren't worth much. At worst, save the speaker (if it's OK) and the valves. The rest probably isn't worth a lot, although the transformers (output especially) may be useful to someone.

BBB2005

ICBM said:

Does the speaker plug in on a cable, or is it hardwired? (Can't remember but possibly hardwired.) If it plugs in on a cable try running it through another cab, that will confirm or eliminate the speaker as the cause. If you don't have access to a cab you're probably best to take it to a tech for a check anyway.

If it's sat unused for some time, was working before, and now isn't, chances are an electrolytic cap has failed - they decay when not used, when they get old. It's probably worth getting it fixed, although I know they aren't worth much. At worst, save the speaker (if it's OK) and the valves. The rest probably isn't worth a lot, although the transformers (output especially) may be useful to someone.

Hi Thanks for the advice.

Tried the speaker and it appears fine. Realised I had changed the phase inverter valve from an RCA 12AT7 to a Mullard a few months ago. So replaced the Mullard with the existing RCA and all appears okay. Combo now has clean back with a nice break up to the upper end.

So presume that was the issue.

Thanks again,

Steve

ICBM

Great!

I forgot that these amps have a valve phase inverter as well, or I'd have suggested to check that! It's quite likely the Mullard has a faulty half (12AT7s are a dual valve) and that would definitely cause low volume and a nasty (asymetrical waveform) break-up. Don't throw it out just yet though, if you haven't already - it's also possible it just wasn't making a good contact with the socket, which would do the same thing.