RECTIFIER TUBE

hdspeakerman · « **on:** 12 Mar 2012, 01:09 am »

I just bought a vintage amplifier and I wanted to listen to it in the dark. With the light out I noticed that the rectifier tube puts out more light than all the other 10 tubes. Tomorrow I plan to borrow a temp gun from work and see what is going on with the temperature. MY question is, " Does this sound normal or is it an indication of a problem that needs to be addressed? I would appreciate your thoughts or opinions.
Howard

Diamond Dog · « **Reply #1 on:** 12 Mar 2012, 01:20 am »

On my Manley 300B pre, the 5AR4 rectifiers definitely "outshine" everything else. I think rectifiers run harder normally ( at least in some designs ) but others here would certainly know better than I... My 5691's by comparison don't light up at all that I can see...sound great, though.

D.D.

AVnerdguy · « **Reply #2 on:** 12 Mar 2012, 01:52 am »

Normal. A rectifier tube has only two elements working at full load all the time whereas the others have multiple grids and are controlling the output by limiting electron flow through the tube.

hdspeakerman · « **Reply #3 on:** 12 Mar 2012, 02:27 am »

Thank you. It does not sound like a problem is a sure thing at this point. I am going to take some temp readings tomorrow for a base line against any future issues. Anyone have any idea about what a good temp would be or a high one for that matter?
Howard

jazzerdave · « **Reply #4 on:** 12 Mar 2012, 02:29 am »

I've used many different 5AR4's. The amount of light produced seems to vary greatly from brand to brand.

I had some Chinese 5AR4 that was incredibly bright. The plates were a bit shorter, so more of the other elements of the tube were visible. That tube also happened to blow up on me.

My NOS Phillips are pretty bright and also have a large portion of their elements exposed. These aren't nearly as bright as the failed Chinese tube, and actually had more of a yellow glow than orange.

My Mullards aren't as bright. They're much more compact, so most of what is visible are the plates.

I also have a Groove Tube that I use when testing changes. It's light output is somewhere between the Mullard and the Phillips.

What kind of 5AR4 are you using?

AVnerdguy · « **Reply #5 on:** 12 Mar 2012, 03:18 am »

Different brands will have different looks (and heat output) as per the previous posts. They will have more brightness but not excessively so. Maybe 2 times brighter is not concerning. However, if they look like a reading lamp 60 watt bulb you might try another. Or, if there is a purple glow (indicates gassy tube losing it's vacuum) it should be replaced. There is no "typical" between brands unfortunately.

bregez · « **Reply #6 on:** 12 Mar 2012, 03:31 am »

There are also directly and indirectly heated rectifiers that glow differently. Just for your reference the 5Y3 rectifier tube (the large tube in the image) runs about 215 F in a Hagtech preamp at idle. Not sure how that will compare to the 5AR4 tube in your amp. I have a Dynaco ST-70 whose 5AR4 (Sovtek) idles at about 320 F. The rectifier tube in these amps are pushed near their limit.

bunky · « **Reply #7 on:** 12 Mar 2012, 03:55 am »

i have a 18wpc 6C33-B SET integrated that i bought from a Guy on Audiogon. i used it with the tubes that he sent with it which were Russian power tubes ,Red metal envelope RCA 5692's and Chinese 5Z3P rectifiers. i tried it and it sounded good but i noticed that the verticle rods in the Chinese Rectifiers seemed to burn really bright i listened for a hour or so and turned it off. the next day i turn it on and it runs for about 20 seconds and i see a spark (AKA) piece of metal drop from the top of the support rod into the bottom of the tube shorting the tube and blowing the fuse in the amplifier

i replace the 5Z3P's with some NOS GE 5U4GB after replacing the fuse in the amp and everything was fine. i currently run matched circa 1944 RCA 5U4's because they are the best sounding rectifier tubes that i have heard out of the five types that i have tried in this circuit.