Egnater tweaker 15 seems to run very hot

[sdcruiser]

I'm a new owner of a used Tweaker 15. It has been modded with the hot foot pedal control option and came with el34's. This little amp seems to crank out a lot of heat for a 15 watt amp. I checked it with a watt meter and it's using 81 watts. My modded blues jr only uses 45 watts and my modded v33 crate uses 84 watts so this seems like a lot power being used and therefor a lot of heat. I tried some 6l6 tubes and it only dropped to 77 watts. The heaters on the 6l6 use a lot less current and I thought this might drop by a lot more. I'm going to try the 6v6 tubes too since they are half the heater current of the 6l6 and should run a bit cooler. I can't tell if there have been other mods at this point since the schematic isn't available but I'm going to be looking at various voltages and current to try to figure this out with or without the schematic. Does any tweaker owner out there have a watt meter to test their head unit? It's so hot that you can't keep your hand on the top grill in one location in the middle above the transformers. Is this normal? It it really is normal it can't be good for things like transformers, etc. Thanks

 

[bruce egnater]

The EL34 tubes draw way more filament current than 6V6, which is not a good thing. Certainly can cause excessive heat and even damage the power transformer. Also, check that the 10 watt output tube cathode resistor is 470-510 ohms. Very early ones had a lower value because the original tubes drew less current. Suggest JJ 6V6 as a reliable choice.

 

[sdcruiser]

The EL34 tubes draw way more filament current than 6V6, which is not a good thing. Certainly can cause excessive heat and even damage the power transformer. Also, check that the 10 watt output tube cathode resistor is 470-510 ohms. Very early ones had a lower value because the original tubes drew less current. Suggest JJ 6V6 as a reliable choice.

You are correct, the cathode bias resistor is 220 ohms. Seems like there is a lot of confusion out there about the correct value and I'm glad you settled it. I actually found a schematic online and confirmed what you stated above and will change out that resistor. I did get a set of JJ 6v6S tubes and the wattage dropped from 81 to about 64, much cooler. I'm assuming the 470-510 is also the correct value for the 6v6 tubes. I just measured the average plate dissipation with the 220 (216 ohms) and it's 15.8 watts, a bit too high. Plate voltage is 354 and about 48 ma current.

I've uninstalled the hot switch pedal mod since that was creating a huge amount of noise and now it's pretty quiet with just some white noise when cranked up nearly all the way.

Looking at the schematic I also noticed that R28 on the preamp board is supposed to be 2.2k but I have a 10 ohm resistor there. It is mounted off the board and does look like it has been modded. Is 2.2K the correct value? Are there any other changed component values in the later boards that I should fix?

Thanks so much for your response. I almost missed it and was happy to see it today. This is a great little amp out of the box.


I did email your customer service about the excessive heat and the responder did not really tell me about the early bias resistor. I specifically asked him too and he wanted me to take it apart and tell him the component number. The 10 watt bias resistor description was not enough for him.

 

[thickwood]

The size of the chassis cabinet needs more room for bigger hotter tubes I think, top of tube too cabinet is critical I suspect !

 

[Roddy]

The EL34 tubes draw way more filament current than 6V6, which is not a good thing. Certainly can cause excessive heat and even damage the power transformer. Also, check that the 10 watt output tube cathode resistor is 470-510 ohms. Very early ones had a lower value because the original tubes drew less current. Suggest JJ 6V6 as a reliable choice.

Bruce, is it ok to run EL34's in a Tweaker 40?