Ceriatone ots, hrm.

[BobW]

Frankie, no disrespect meant here, but you may get your amp issues resolved quicker by taking it to a repair shop. It seems you are wanting to learn more about amplifiers, which is a good thing, but the HRM is even more difficult to tweak for best tone than it is to diagnose a loss of signal issue. It will be a long and arduous task to do this since you are still having difficulty diagnosing the problems with your amp.

This forum is filled with a lot of knowledgable people who want to help you, but having a working amp, then deciding how you want your tone to sound, (more/less bass, treble, gain, etc), is where this forum can really help you. Although a lot of valid suggestions have been offered, it's sometimes difficult to diagnose a problem such as this via emails only. A hand's on help may solve your problem(s) quicker.

However I do have a few questions for you: Have you validated the drop out issue is really present in two for your amps and was not related to anything common to both such as using a common speaker enclosue, speaker cables, guitar cable and guitar?
Is your amp stored in a basement where there is a high humidity content? If yes, then moisture may be the problem. Move it to a low humidity area.
Is the 2nd amp a purchased amp or also home built? If yes the common thread may be a build issue. (questionable solder joints, oscillation, under rated components, eg: 1/2W used instead of 1W screens, etc, etc)

sorry for the rant, but hope this helps you fix the issues. cheers!

[Frankie]

Just to remember. My hrm amp sounded good for a month, used it at six gigs, every day practice. So the issue showed up many hours after I built it. The amp was tweaked ready. Didn`t take it out of the cab during that time, so something has started to fade out by it self here. Maybe it can be the PT tranny then. That is the org ceriatone tranny. The OT is changed after the issue started, also the choke. I maybe need to buy a PT and try some day.
I have soon spent so much money on this one, that I could have bought a Two Rock instead. ha ha. ;)

[Structo]

Bob has a point, there must be something common between the two amps for them to have the same problems.

That would be quite a coincidence for them both to have faults at the same time that exhibit the same symptoms.

I believe you mentioned that you did try a different speaker cab?

Try to think outside the box. What is common to both amps when playing?
Speaker?
Guitar?
Cords?

I had a bad speaker cable before that almost made me believe my OT was going bad.

Another thing that has bothered me is some high frequency fizz. I have come to the conclusion that it is most likely my ears, since I have some tinnitus, because all my amps start to sound fizzy after a while......

[Frankie]

Bob has a point, there must be something common between the two amps for them to have the same problems.

That would be quite a coincidence for them both to have faults at the same time that exhibit the same symptoms.

I believe you mentioned that you did try a different speaker cab?

Try to think outside the box. What is common to both amps when playing?
Speaker?
Guitar?
Cords?

I had a bad speaker cable before that almost made me believe my OT was going bad.

Another thing that has bothered me is some high frequency fizz. I have come to the conclusion that it is most likely my ears, since I have some tinnitus, because all my amps start to sound fizzy after a while...... :?

Have tried different cables, guitars, speakers, tubes etc.
I use the cab for my bruno, and this never happens to that amp, done gigs for 2,1/2 years with that one, and never failed. :) Not my ears either!
The strange thing is when I wait some minutes the sound is big again, and after playing it fades to get hard again, and with less volum! Wait again and it builds up again. Don`t have to turn off the standby to have it back to the big sound again, just waiting a while. Odd problem. The other amp works well now, but had that problem before. It`s just that I don`t know what I did to make it get rid of the problem, cause I changed so many things on that one. Tried it yesterday with the same speakers, cables, ,guitar, and it it is steady. So it must be something in the HRM amp that is the problem!!!!!

[llemtt]

It's indeed a very strange kind of a problem!

I can't remember if you already said that everything happens even if you connect the HRM preamp to another power amp of yours, can you confirm?

Does your PT gets hotter while the problem builds up?

[Frankie]

It's indeed a very strange kind of a problem!

I can't remember if you already said that everything happens even if you connect the HRM preamp to another power amp of yours, can you confirm?

Does your PT gets hotter while the problem builds up?

It happens in both the power and pre amp. I have tested with the pre amp, and power amp from the bruno cowtipper.

The PT is not getting hotter at that moment, but I`m starting to believe it must have something to do with the power, cause I have changed so many parts in the amp. Changed bass, and mid cap today. same problem still there.

[BobW]

Another thing to consider, Check your house voltage. Maybe you are experiencing an intermittent ground at the power companies stepdown transformer. This would cause a voltage imbalance +/- and -/+ on both sides of the CT grounded stepdown secondary. You will need to monitor it as long as it takes for your amp to drop in and out.
It's a remote chance this is the problem but would explain why it's hapening in both amps.

[llemtt]

Another thing to consider, Check your house voltage.

Yes of course but anyway he has a Bruno cowtipper perfectly working, and he doesn't measure anything significant relative to the supply voltages.

One thing I still continue to suggest: use a scope because readings from DMM are often misleading, if there is something happening in the Mhz frequency domain there's no DMM that can show it to you. Consider that such an high freq event can cause transformers cores to saturate, relays malfunctions,...

But if it can be confirmed that the following configuration

OTS Clean Preamp + cowtipper power amp

reproduces the problem, then I will concentrate on the OTS Clean Preamp because it's easier.

cheers
Teo

[Frankie]

Another thing to consider, Check your house voltage.

Yes of course but anyway he has a Bruno cowtipper perfectly working, and he doesn't measure anything significant relative to the supply voltages.

One thing I still continue to suggest: use a scope because readings from DMM are often misleading, if there is something happening in the Mhz frequency domain there's no DMM that can show it to you. Consider that such an high freq event can cause transformers cores to saturate, relays malfunctions,...

But if it can be confirmed that the following configuration


OTS Clean Preamp + cowtipper power amp

reproduces the problem, then I will concentrate on the OTS Clean Preamp because it's easier.

cheers
Teo

Yes It happens with the ods clean preamp + cowtipper Power amp.
But it also happens with the cowtipper pre amp + ods power amp, so Its global problem. It must be in the power tranny in some way, can the PT saturate in parasite oscillation and cause this problem?

[llemtt]

can the PT saturate in parasite oscillation and cause this problem?

honestly actually I don't know for sure, I think PTs rarely suffers from their own high freq oscillations

a most common saturation situation occurs with "eddie-currents" that are caused by bad lamination insulation (laminations should not behave as conductive "rings")

PTs indeed can suffer from high freq oscillations born elsewhere and injected into their windings, but I never experienced such an event

as you say it should be a global problem affecting both preamp and poweramp tubes and the things they easily share are supplies (DC and heaters) and grounds so these are prime suspects, they have to be checked relative to both oscillations and saturation problems

anyway PT saturation turns into a reduction of his current supply capability and heating

given that the OTS preamp + cowtipper configuration doesn't draw significantly more current from OTS supply while playing (make sure there's no signal getting into OTS poweramp...), and you said the PT doesn't get any warmer, PT saturation is not my preferred suspect

[mcinku]

Just one more idea...
Once my friend experienced strange behaviour on his amp... it was working fine but then sudden loss of power occur... if my memory still serves me well
Anyway... at the end it was a bypass switch... somehow it was loosing connection... like it was going on and off real quickly due to amps vibrations.

It's a long shoot but still worth checking.

[v00d00blues79]

have you tried a small jumper cable between the pre-out and power amp-in on the passive loop? this could cause some weirdness to happen.

Just a suggestion that I didn't see already.

Thanks,

Andy

[Frankie]

Thanks to all you guys for help and suggestions with my amp so far, I`m still fighting this beast to make it work properly.
Frankie. ;)

[massygt6]

I had an issue similar to yours that sent me mad for about two weeks...it was the shielded cable from the input to the first preamp tube...check it out.

[mojotom]

I may be wrong but on my newly build 124 the amp start to sound better when it's warm and even better when played for 30 mn or more. At that point the PT is quite hot to the touch so the amp ask the PT to deliver a good amount of current. I'm using an Heyboer Mojotone PT and an old 75 twin OT and the PT is oversized.
I think you could try to change the PT, Leo was cheap but more so for Ceriatone. It could be the PT not being able to supply enough current when hot (running for a while)