Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: john_t on August 30, 2010, 02:21:49 pm

Title: MY schedule 40 runs hot
Post by: john_t on August 30, 2010, 02:21:49 pm

I noticed my schedule 40 runs pretty hot. Upon further inspection I realized I had a 5y3 rectifier tube (Sovtek) instead of the 5v4 the schematic calls for. Would this make the amp run hot. No other issues with the amp. Sounds really good.

Title: Re: MY schedule 40 runs hot
Post by: jojokeo on August 30, 2010, 02:51:02 pm

Negative, if you can run a 5V4 then you can run a 5Y3 - it's only 2A @ 5V.

Title: Re: MY schedule 40 runs hot
Post by: rafe on August 30, 2010, 07:38:23 pm

How hot? Can you put your finger on it and count to 10 ? :angel

Title: Re: MY schedule 40 runs hot
Post by: john_t on August 30, 2010, 08:22:22 pm

the chassis near the tubes gets way hot. Yes to hot to keep your hand on for more than a few seconds. You can put your hand on the transformer. I think it is just the heat generated from the el84 power tube. The tube is not glowing red but I can just feel the heat coming off it big time . Is there a tube socket that would transfer less heat.  I put a fan near the back of the amp and it cooled it right down. Iam thinking of installing a small dc fan just to move some air around the tubes. Is this normal. The amp seems to  run and sounds find. thanks for the help

Title: Re: MY schedule 40 runs hot
Post by: john_t on August 31, 2010, 11:22:54 am

I checked the tranny on my vintage GA-5 ,the tranny gets just as hot. I also have a Fender Champion 600 The new one. The tranny on that is putting out about same amount of head. I guess am worried about nothing. Any thoughts on a small dc fan.

Title: Re: MY schedule 40 runs hot
Post by: rafe on September 01, 2010, 01:38:18 am

I tried to post back the other day but couldn't some glitch with the site. Tubes get real hot and as long as they are biased right and aren't redplating they are good...I have a 61 ga5t it runs pretty hot, but I'm not too concerned, as a matter of fact I was missing the top back piece and made one out of pine (closing the back more than stock) it really improved the sound but it runs a bit hotter.....I was worried about the tranny on a fender I have, it too is hot about 5 seconds and I take off my fingers ....I play it all the time and it hasn't let me down in 4 years, fan or not that's your call ......I'm not too worried myself, hope that helps

Title: Re: MY schedule 40 runs hot
Post by: john_t on September 01, 2010, 10:21:54 am

Thanks for the reply. I feel a little better.  I just did not realize the amp ran that hot. I guess its normal

Title: Re: MY schedule 40 runs hot
Post by: john_t on September 01, 2010, 10:24:45 am

If some one out there has a schedule 40 GA-5 build with a el84 power tube could you post your voltage readings. I would like to compare them to mine.