The Amp Garage

What do you amp repair guys do in a case where 1 of 4 matched power tubes needs to be replaced. Do you replace all 4 or try to find a single tube the matches the other 4?

Thanks,
Don

Just wanted to follow up. The issue was indeed a bad power tube. Thanks for all of the tips and information!

Don

martin manning wrote: ↑Fri Mar 03, 2023 5:10 pm Low frequency buzz could be failed/failing rectifier. That will usually take the mains fuse out, but it's something to be aware of.

Thanks Martin! I will certainly look at that.

WhopperPlate wrote: ↑Fri Mar 03, 2023 4:14 pm
This is the common troubleshooting process of elimination. The PI tube is most likely suspect if master volume doesn’t effect anything. Pi is downstream.

Got it. Thanks for the response Charlie!

bepone wrote: ↑Thu Mar 02, 2023 9:04 pm pull the PI tube out and verify the oscillation stop

Thanks bepone. This is an interesting suggestion. Do you suspect that the PI tube is causing the oscillation or is this just a good way to isolate the preamp from the power amp?

The voltage ratings of the components are usually high enough to take unloaded (tubes out) voltage levels, but there are no guarantees. Do you have a lightbulb limiter? A low-wattage bulb would knock the voltage down to a safe level. Thanks Martin. This makes me feel better about removing the power...

I built an ODS a few years ago. I was playing the amp yesterday and all of the sudden there was a loud, obnoxious, constant noise or oscillation. Even with the master volume turned down all the way, it still persisted. Banging the top of the cabinet (not too hard) with my open hand changed the volum...

Very cool picture! Do you have any info as to what was going on there?

Rick Beato makes a pretty good podcast/youtube video. In this video he is taking a closer look at a guitar solo from a hit song that got lost in the mix. When he isolates this track at 5:55 my ears hear delicious Dumble tone. This is the kind of tone that I was looking for when I discovered Dumble a...

The image below was supplied by Tony in a previous post. It is how Dumble implemented a strat switch. The way I interpreted this is that a 2nd mid capacitor is put in series with the mid capacitor that resides on the pre amp board. This 2nd cap is soldered to a mid pot that contains a push/pull swit...

Can anyone point me to a recording of #123 or even a recording of a #123 clone?

The HRM is inconvenient to adjust in an ODS just the same but people keep including them in their builds as small boards with trimmers tucked inside the chassis. The narrow panel tweed seems a bit more convenient to access since you can just take the back panel off. General discouragement aside, I ...

Charlie Wilson wrote: ↑Sun Feb 06, 2022 4:23 am All of the real Dumbles I have had my hands on were biased pretty warm by him.
CW

At what percentage did he tend to bias amps?

Was Tremonti who it was originally built for or did he buy it from someone else? The amp is from1995 which puts Tremonti at 21 and Creed's first album didn't come out until 1997.

If you like hearing stories about Dumble you will like this podcast. There is a lot of interesting information in this. Richard McDonald from Fender talks about his friendship with Dumble. Starts at 15:10 in the following episode of Guitar Wank: https://www.guitarwank.com/podcast/episode/4b8c4d05/gu...