Ceriatone ots, hrm.

[Frankie]

The platform of both my ots, and hrm are ceriatone.
Both amps sounds best the first 15 minutes of playing, then they gradually are getting harder, and loose the juice. Swapped out all the tubes, changed OT to TADS om 50. Changed the lyt.. caps to tad. Tried different lead dressing. Float the filaments above the tube sockets.
Cant find the problem, anyone who can help PLEASE!!
The amp take stomp boxes very good befoer it loose the juice too! :(

[ChrisM]

Something is overheating.

Check resistors, caps (especially ceramics).

Measure the voltages after start up and after 15min (or whenever the tone goes downhill). That will be a good determining factor.

[talbany]

Can you be a little more descriptive than getting harder and loosing juice..

Tony

[Frankie]

Something is overheating.

Check resistors, caps (especially ceramics).

Measure the voltages after start up and after 15min (or whenever the tone goes downhill). That will be a good determining factor.

The voltages are the same when the amp is getting harder ( nearly only upper mids left). If I turn off the standby for some minutes (10 min), the amp sounds good for a while again!

[ChrisM]

A heat issue then.

[Frankie]

A heat issue then.

Any suggestions what can be wrong here, or how to find the trouble?
Nothing of the components are specially warm in the amp.

[bcook]

This happens on 2 different amps exactly the same? What is your mains power situation?

[Frankie]

This happens on 2 different amps exactly the same? What is your mains power situation?

No this happened a year between them.

[Frankie]

This happens on 2 different amps exactly the same? What is your mains power situation?

Sorry. Yes both my ceriatone D*** got the same problem.
I can also hear on other youtube clips the muddiness that other ceriatone D*** have. Kind of a blanket over the amp. But mine are fine for a while, before they gradually turn into cheap sounding amps without any headroom. :cry:

[Structo]

Did you build these amps from a kit or did you receive them fully built?

What you are describing really doesn't make a lot of sense.

How is your hearing?

I have bad tinnitus that sometimes makes any of my amps sound like crap.

If it is the amps, check all solder joints and grounding.
How are the tubes?

If this is happening to two amps, look for what is the commonality between the two.
What did you do the same on both amps?

[talbany]

If the amp loses headroom goes cold gets gravely and develops a nasty type distortion.. I would look at the output section first (If your sure it's the amps)...You need to look at where the tubes are biased at the time of the event first.....Make sure your bias is not drifting..

If your playing the amps through the same cabinet...
and your speakers can't handle the power or volume your feeding them they begin to heat up lose gauss and the effect can be what you are describing as well... This also takes place around the same time frame you are describing.This one to me makes the most sense being you are getting it in both amps...Good Luck!!

Tony

[BobW]

I agree with Tony, but if the bias is Ok, using a heat gun w/ a pointed nozzle and aimed at suspect ceramics can help locate a problem cap. No need to dwell too long, since a questionable cap will become apparent.

[Frankie]

Did you build these amps from a kit or did you receive them fully built?

What you are describing really doesn't make a lot of sense.

How is your hearing?

I have bad tinnitus that sometimes makes any of my amps sound like crap.

If it is the amps, check all solder joints and grounding.
How are the tubes?

If this is happening to two amps, look for what is the commonality between the two.
What did you do the same on both amps?

I have built these amps myself, and there are different trannies, different tubes, caps, resistors. But the power tranny, and those eyeleted boards are the same. I have tried maybe 30 different tubes.
Many different guitars, different cables, speakercables, maybe I played those amps for a month before they started behave like this.
I have also played them around on gigs, so it`s not my wall electr... either.
And my hearing is extremely good. (Maybe that`s the problem he he).
You can also feel the change in the amp. The touch response is also fading away with the sparkle.

[Frankie]

If the amp loses headroom goes cold gets gravely and develops a nasty type distortion.. I would look at the output section first (If your sure it's the amps)...You need to look at where the tubes are biased at the time of the event first.....Make sure your bias is not drifting..

If your playing the amps through the same cabinet...
and your speakers can't handle the power or volume your feeding them they begin to heat up lose gauss and the effect can be what you are describing as well... This also takes place around the same time frame you are describing.This one to me makes the most sense being you are getting it in both amps...Good Luck!!

HRM
The bias is 33ma, and the plates are 485 v.
EL34.
ODS
The bias is 40 ma, and the plates are 440 v.
EL34.
The bias is not drifting on non of them.


Tony

[ampdoc1]

Ear fatigue? Have you tried playing other amps and see if you hear a change at about the same time?

a'doc1