how hot is too hot :)

martin manning · Post by **martin manning** » Tue Apr 07, 2020 10:44 am

So you are probably running them pretty hot re the usual 60-70% dissipation. I think a fan would be cool, though (Ba-dump-bump), and would extend component life. My D amp gets pretty hot after a couple of hours too.

norburybrook · Post by **norburybrook** » Tue Apr 07, 2020 11:33 am

martin manning wrote: ↑Tue Apr 07, 2020 10:44 am So you are probably running them pretty hot re the usual 60-70% dissipation. I think a fan would be cool, though (Ba-dump-bump), and would extend component life. My D amp gets pretty hot after a couple of hours too.

I think I've a set of 6L6's lying around I'll put those back in and see how it is, it is on all day after all

. Had the amp not been covered I'd fit a fan to the floor of the cab to draw cool air in. You'd not see it and that would be a good solution. I think a vented front panel would help as well. Just dont know if I can be bothered to pull all the staples out and re do it

Thinking about it, the donor peavey combo had a small fan in the side blowing air into the chassis.

M

martin manning · Post by **martin manning** » Tue Apr 07, 2020 11:44 am

Seems to me I saw a photo of a D amp with a fan mounted on the bottom of the head cab. You already have a cutout in the front panel, no? A small muffin fan could push air out through the grille cloth. You could test that idea out pretty easily, powering the fan from some external source just to see how effective it is. For a permanent installation I would power the fan from the AC mains, maybe even use an AC adapter.

norburybrook · Post by **norburybrook** » Tue Apr 07, 2020 11:58 am

martin manning wrote: ↑Tue Apr 07, 2020 11:44 am Seems to me I saw a photo of a D amp with a fan mounted on the bottom of the head cab. You already have a cutout in the front panel, no? A small muffin fan could push air out through the grille cloth. You could test that idea out pretty easily, powering the fan from some external source just to see how effective it is. For a permanent installation I would power the fan from the AC mains, maybe even use an AC adapter.

No, front panel is solid. Dumble seems to do solid front panels from the pics I've seen. I noticed that the newer cloners like two rock have a frame so air can flow through. I made my JM wonderland like this.

M

talbany · Post by **talbany** » Tue Apr 07, 2020 12:53 pm

IMO there are 2 kinds of hot?. 100W fixed bias run loud then there is Cathode biased AC-30 /5E3 Deluxe hot

Now those amps run HOT! Some of my best sounding amps have seemed to want to run on the warm side.

Marcus. I really wouldn't worry about changing out tubes. Just throw a little fan in it when you get a chance. I am sure it will be fine

BTW. Does that amp have a FWB rectifier on the P.T??
Tony

norburybrook · Post by **norburybrook** » Tue Apr 07, 2020 1:01 pm

talbany wrote: ↑Tue Apr 07, 2020 12:53 pm IMO there are 2 kinds of hot?. 100W fixed bias run loud then there is Cathode biased AC-30 /5E3 Deluxe hot
Now those amps run HOT! Some of my best sounding amps have seemed to want to run on the warm side.

Marcus. I really wouldn't worry about changing out tubes. Just throw a little fan in it when you get a chance. I am sure it will be fine

BTW. Does that amp have a FWB rectifier on the P.T??
Tony

yes it does, it's running a B+ of 500V

The tubes are all over the place actually now I've measured them. So Some were running very hot some not so. I've knocked the bias back so the maximum is around the 60-65% on the minimum is quite cold. I can't remember how well they were matched when I got them, i think they were not that well matched despite having being tested and had stickers on showing some sort of value. At the end of the day this amp has always sounded great so I've not really thought too much about it until recently when I noticed after a day of sessions it was really hot when I went to turn it off.

bluesmaster.jpg

thanks for all the advice.

i now need to go fix the dishwasher it seems................ as my old dad used to say 'it never rains but it pours'

M

martin manning · Post by **martin manning** » Tue Apr 07, 2020 2:51 pm

"When it rains, it pours" is the adage here. Try swapping the tubes around to better balance the idle current side-to-side if they are not well matched.

Below is what I'm thinking for the installation of a small cooling fan. No additional cutouts or removing/replacing of covering or grille cloth required, and you could attach the fan power supply to the panel that the fan is attached to. I think it's better to push air through the cloth from the inside to avoid collecting dust on the outside.

Is this the cab? https://ampgarage.com/forum/viewtopic.p ... 94#p386594 So I guess you'd need a new front panel. You could whip one up in an hour, couldn't you? ;^)

norburybrook · Post by **norburybrook** » Tue Apr 07, 2020 3:01 pm

martin manning wrote: ↑Tue Apr 07, 2020 2:51 pm "When it rains, it pours" is the adage here. Try swapping the tubes around to better balance the idle current side-to-side if they are not well matched.

Below is what I'm thinking for the installation of a small cooling fan. No additional cutouts or removing/replacing of covering or grille cloth required, and you could attach the fan power supply to the panel that the fan is attached to. I think it's better to push air through the cloth from the inside to avoid collecting dust on the outside.

yes, that looks great but my front panel is solid so I'd need to remove the vox grill cloth and cutout an opening

I've never hear the term 'muffin fan' before . I shall now google it.....

dishwasher is knackered by the way. Broken glass had got past the filter and broken the pump!

it's certainly been pouring this year so far!!

M

martin manning · Post by **martin manning** » Tue Apr 07, 2020 3:14 pm

As I said above, I'd just make a new panel if you go for it. Looking inside my head box it's going to have to be a small fan to fit between the transformers, Maybe a 3".

alkuz1961 · Post by **alkuz1961** » Tue Apr 07, 2020 4:24 pm

I prefer to put two identical fans and connect them in series. This connection reduces the speed of rotation and reduce noise. But the efficiency is not reduced, since the air flows through two fans. And two fans can be installed on both sides of the chassis

norburybrook · Post by **norburybrook** » Tue Apr 07, 2020 4:50 pm

ah...in my box of bits i've found these

fans.jpg

Perfect.

I think IIRC my relays are powered from an extra tap on the peavey transformer that I dropped down to get 12v so I think it might be worth a go hooking either the 2 small or one large and see if it's ok. Be nice not having extra transformers/wiring. I could fit a small on /off switch on the chassis underside by the voltage regulator.

M

mojotom · Post by **mojotom** » Tue Apr 07, 2020 4:59 pm

martin manning wrote: ↑Tue Apr 07, 2020 11:44 am Seems to me I saw a photo of a D amp with a fan mounted on the bottom of the head cab. You already have a cutout in the front panel, no? A small muffin fan could push air out through the grille cloth. You could test that idea out pretty easily, powering the fan from some external source just to see how effective it is. For a permanent installation I would power the fan from the AC mains, maybe even use an AC adapter.

I think it was the blue suede SSS.

I noticed quite a high temperature on the ODS head, these are quite small for a 100W, top chassis mounted and the PT gets hot too (NOS or new) but I felt the amp sounded better after a few hours of burning time.

alkuz1961 · Post by **alkuz1961** » Tue Apr 07, 2020 5:58 pm

Marcus, try not to place the fan next to power tubes, and direct the air flow past the lamps, but not at them. Direct exposure to cold air can cause cracks in the glass.

martin manning · Post by **martin manning** » Tue Apr 07, 2020 6:01 pm

There is very little room on the power side of the box, I think a 3" (80mm) fan might fit right between the PT and OT, and pull air in and across the power tubes. Removing the front panel would allow you to easily see if it will fit with the chassis installed. I would wire it with the main ac power in the amp so it would turn on with the main power (along with the heaters), which would be the case if you can get enough current from your relay supply. You could also consider running it on reduced voltage to lower the noise.

Mojotom, yes that was it.

norburybrook · Post by **norburybrook** » Tue Apr 07, 2020 6:19 pm

I was thinking about mounting the 120mm fan on the cabinet floor @90 deg to the tubes so I would blow air across the chassis transformers and power tubes.

It would also be quite unobtrusive visually mounted this way.

M

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