henry4841

It was recommended for sure. By their very nature the hotter you run a transistor the better it is going to sound. You would need to look for crossover distortion on a scope to be certain if lowering some more would hurt but I from experience I would not be afraid to lower it to 15mv if I did not here any difference in sound without looking at a scope. At 15mv the transistor is not cutting completely off going into class B. The non working transistor of the sine wave would still be running some. Just guessing, not looking at the schematic or circuit, I would think you would have in the neighborhood of 20 or 25ma of current running in the transistor at 15mv bias. If it still sound fine and lowered the temp I would give it a try. He really needs to check the temp with a temp gun to determine what the temp really is. It might not be as hot as he thinks. I have a number of class A amplifiers running at 55 to 60 degrees Celsius and at 60 degrees you cannot touch the heatsinks for longer than a couple of seconds. That is what I call running hot.

Youtube is you friend in the 21st century. From beginner to engineer. Uncle Doug is not a bad place to start for tube circuits. https://www.youtube.com/channel/UCuR4hQTXkG_KxozLxwPzEjQ There are many like him also on youtube but he is a teacher by trade and does a good job for a beginner to learn from. At least from memory says he is, was a teacher. It is always good to have a teacher than just reading a book not that there is much to learn from reading a book as well.

Not really too sure at what temp they are suppose to run at idle after doing some googling but I would measure the temp with a temp gun and would not worry too much about it if it was 125 degrees or less at idle. What I was searching for was it run in class A and could not find any answer which leads me to conclude it was A/B. The heat tubes were there because the power transistors are on the board and not separate from it like most amplifiers. Selling point to impress without any measure of being better just because of being n board. It would not hurt anything to lower the bias to say 15 mv if the heat concerns you. All bias does if prevent power stage from going from A/B to just B. In other words keep it from having crossover distortion. As long as the bias idles the transistors above cutoff it really does not matter that much what it idles at. If you lower it too much you will hear the distortion which is very unlikely at 15 mv or even lower.

Just thought I would add. my brother with heart problems and overweight had planned surgery and caught virus in the hospital. Was sick for 3 days and came back strong without any problems. Hard to figure out if you will make it if you get it. Here this week and gone tomorrow if you are like me in your senior years. Both of them including me are ,were around 70 years old.

My best friend died from Covid-19. No known health problems before virus. Sick on Wednesday, found dead following Wednesday. Lived by himself as I do.

I would have seller's remorse over that one myself. Almost as much as selling my 73 Triumph 750 for $650. https://classicreceivers.com/yamaha-cr-2040

Instead of saying warmer I would rather say more lush sounding, at least some of them. One has to remember when comparing tube vs SS that there are very few SS single ended amplifiers. Most are push pull which sounds very different that single ended SS amplifier. I have both single ended and push pull SS amplifiers and the SE could be called warmer sounding than their push pull SS ones. And the majority of tube amplifiers are single ended with just one output tube per channel. When one compares a quality built push pull tube amplifier with an comparable built SS push pull amplifier the difference in sound is not so prevalent. A SS single ended amplifier has a sound much like a single ended tube amplifier. I like the sound of both depending on the mood I am in and the music I am listening to. Before one can truly say a tube amplifier is warmer sounding they need to listen to a SE SS amplifier. Firstwatt has made some in the past and has one, the F8, for sale now.

Probably house brand for some dept. store made by some of the name brand makers of receivers. I just bought a house brand JC Penny receiver called Modular Component Systems a MSC 3233. After some research I narrowed it down to a couple of big name makers. Looking at some inside pictures it looks like a nice quality receiver with good parts. Never will have the resale value of Marantz or Pioneer but I am expecting it to sound good after a refurbish.

Hint, Can't remember S***

And the one I liked the best. https://worldradiohistory.com/Archive-All-Audio/HiFI-Stereo-Review.htm This site is a gold mine of ancient text. https://worldradiohistory.com/

Thanks for finding this.

Sure did and the vintage speakers command a big price now.

I would have a hard time finding where I located this file. I do it all the time, look for a file I saw online and trying to find it again. I found it very interesting myself being a child of the 60's and 70's and waiting for all the rags new issues to come out. I still have some of them now but most got lost in moves and etc. What was impressive to me was in 1957 there was 215 pages. That changed in the 60's and 70's to less and less pages and price increases. There was a market way back them for diy'ers to buy and assemble kits which has virtually vanished now. One can still find kits from China but very few in the USA. I remember building a television kit and multiple meters and pre-amplifiers. Now I build mostly from just a schematic. Equipment kits are one thing that has vanished. The kits from that era bring premium prices on Ebay now.

Found this googling this morning. HiFi was expensive compared to todays prices. https://worldradiohistory.com/Archive-All-Audio/Archive-High-Fidelity/50s/High-Fidelity-1957-Oct.pdf High Fidelity magazine October 1957

Do some homework and see what is involved in cleaning the pots on that particular receiver. Some receivers are very simple and some are a PIA and the pots have to be removed from the circuit board to clean them properly. Do not spray unless you are doing it correctly because you do not want it all over the circuit board. AudioKarma may have some info along with hifiengine. https://www.hifiengine.com/manual_library/harman-kardon/430.shtml Download the service manual. Like Dr's do no harm.