MV45 running too hot

[4thtimeaudiophile]

I know that the MV45 will run hot because it is a tube amp. But.....everything gets hot including the chassis. It is more than just warm to the touch. The EL34's are good and they hold bias as well. There is some mechanical hum which I attribute to transformer delamination, due to its age. It sounds fine also. There is very little noticeable white noise and hum coming from the speakers. I am sort of scratching my head on this one. All of the obvious problems seem to be ok. I read somewhere about checking the screen voltage on the EL34's. If I could understand the theory just a tad bit better, I might be able to get pointed in the right direction. Do any of you fine folks have some ideas about where I might begin poking around to track down this excessive heat?

[AnotherJohnson]

Are the transformers hot? Delamination is a step toward a short.

Is there a ground issue? A ground loop involving the chassis can heat up the chassis.

[4thtimeaudiophile]

I forgot about the ground loop possibility. Even though the MV45 uses a 2 wire power cord, there could still be something wrong there. So, there is no connection to the AC mains service ground on the chassis. However, I could have an imbalance on the two legs of my AC mains. There could be some DC on one of the legs. A "DC Scraper" circuit on the line for the MV45 might help with that. There are other types of ground loops as well. I noticed in a previous configuration of preamp and tuner, I was getting some hum. Time to look at my main power again.

[admin]

If you think there is excess heat, it would be interesting to get the total power draw at idle of your MV45 and compare it to somebody else's. This would at least tell you if the overall heat dissipation is correct or not. An even better step would be to take measurements of the surface/components/power supply via a thermometer heat gun. But of course this all requires another MV45. There are no official specs published on how much heat certain components should reach or even overall power use (as far as I know).

The next step is a thorough component inspection. Anything look like it's burning out, etc.

Ground loops are an entire other issue. It should not be related to excessive heat (presuming the unit does not have a fault).

[AnotherJohnson]

Ground loops are an entire other issue. It should not be related to excessive heat (presuming the unit does not have a fault).

Ground loops ALWAYS generate heat somewhere unless the components have zero resistance.

The OP recognizes that it could be a fault in his 4 decade old, old time floating ground amp and he’s going to check it out.

There may be no specs, but good advice might be ask Roberto.

Other good advice would be to put it on something fireproof and don’t leave it unattended. If it were mine and I thought there were a flaw, I would put it on the bench or take it in. I think he’s already got it on the bench.

From his answer, I think he knows that the flawed ground idea is legitimate. All ground loops are not audible.

[admin]

Ground loops are an entire other issue. It should not be related to excessive heat (presuming the unit does not have a fault).

Ground loops ALWAYS generate heat somewhere unless the components have zero resistance.

Perhaps my electrical knowledge is lacking here, but I always thought that ground loops are very low current and thus there would be no appreciable power consumption (and thus heat production). From a pure physics point of view, sure any current on any resistance is going to produce heat, but from a practical standpoint it would not make a large metal housing on an amp feel noticeably warm to touch. Am I mistaken on this?

[AnotherJohnson]

Ground loops are an entire other issue. It should not be related to excessive heat (presuming the unit does not have a fault).

Ground loops ALWAYS generate heat somewhere unless the components have zero resistance.

Perhaps my electrical knowledge is lacking here, but I always thought that ground loops are very low current and thus there would be no appreciable power consumption (and thus heat production). From a pure physics point of view, sure any current on any resistance is going to produce heat, but from a practical standpoint it would not make a large metal housing on an amp feel noticeably warm to touch. Am I mistaken on this?

Ground loop current depends on the potential difference between ground planes as well as the loop’s (closed circuit) impedance.

In the MV 45 (not grounded to the house via a modern chassis ground) it could be anywhere.

In what you’re used to hearing, it may be a few millivolts.

[roberto]

Hola,
I think AJ nailed. Due to the age of the amp, I think you have a bad power transformer. Excessive heat usually the culprit is the power transformer. Fresh caps in the power supply will get rid of that hum, small signal tubes produce the white noise. Sorry being the bad news guy. You might find a place that can re-build the power transformer. You might try this site:

https://www.heyboertransformers.com