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howdy, got this one I am working on and it, after a recap, is sounding pretty good, only problem is the FM doesn't work so well. Can't find any service info on this model, I do have a schematic which matches my unit, only problem is that the schematic, factory Sherwood one, is inaccurate, there are voltage markings for some of the tubes that are just plain wrong or don't make sense, same for some resistors. This has me chasing down all kinds of stuff and just not know what the hell is going on with this, whether it is a problem or just plain wrong on the schematic. Thanks
Follow Ups:
Michael, did what you recommended, which made sense, but the FM sounds like shit, drifty as hell, hum on the lower band, no operation by the indicator tube or the stereo light. There are several tubes that are showing odd voltages, that is assuming the damn schematic is correct, in particular2nd 6AU6, pin 7=0 v; 12AT7, pin 7=-.72v; 6AU8 pin2=0v; 6EA8 (which is the only weak tube in the set, all others tested) pin3=60v; and finally 6EU7 (in the stereo decoder) pin7=210v. Question, do the ceramic caps ever good bad or leak? In my experience I have not seen that, but this amp is full of them, and some are going to ground in those areas to ground... thank, Randy
Randy
I think you may have gotten some on the plate or plates next to the shaft and it may take a couple days to evaporate.Did you use D5 deoxit?.That's what you want to use because that usually evaporates within a couple hours..Now,if you have some compressed air,try blowing some air around the area on the plate next to each area where you cleaned and lubed..This needed to be done because these tuners are opened and exposed.
A gassy tube or weak tube throw the voltages off or alignment on some of the tubes..Lets just work mono position for right now..
Take a Q-tip and just hold it against each the areas you cleaned and lubed while rolling the tuning dial from one end of the band to the other.
Do this first.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/05/16
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I just saw this post. I had 3 s8000s. One had a problem with fm stereo, distortion but mono was fine. Have you tried fm mono setting in selector switch.
David
Clean and lube all 8 sections but not the plates,just where the shaft goes thru the holding section on both sides..I didn't show all 8 in pictures but you get the idea.
Randy
The biggest problem with FM tuners is one,you need to clean the tuning shaft on the tuning cap that holds the plates with a little D5 deoxit.Do it only on the shaft where it goes thru the 4 sections of the tuning cap..Don't get it on the plates if you can help it..Let it dry for about an hour and then take some machine oil and put a drop on each part of the shaft as you did with the D5 while turning the tuning dial.The reason this is important is because this creates the path to ground for that shaft and you will lose sensitivity..The other thing you need to do if the tubes are good is an alignment...Do you have an FM stereo Generator? Lets see if we can get it working first tho. Make sure you have enough B+ voltage to the RF amp and mixer and make sure you have an antenna wire on that's at least 5 feet long. I may do a youtube video on aligning an FM tuner.
Also,clean the tuner and IF sockets and tighten any loose pins.I would spray D5 or tuner cleaner in the sockets and clean them...This is important before you do anything else as it's typically common place with these tube tuners.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/02/16 06/02/16 06/03/16
Michael, thanks so much, I will give this a go tonight! I know the set was a bit grimy when I got it so its pretty certain the tuning cap is dirty as well. And I would love an FM alignment video, I picked up a Heathkit FM stereo IG-37 which I am planning on restoring for use, and at Kutztown I picked up a Supreme Genescope Model 480, which I also look to get working soon for doing FM alignments! Thanks, Randy
Great info Mike! I would be very interested in see a YouTube video from you. I have a Scott 350D that deserves a rebuild. Supposedly it is a very nice tuner, although it does not seem to command much resale value. I would be building it for personal use, regardless, so who cares! I have a few great solid-scrape tuners, but I'd like to here tube FM in all of its glory.
Dave
I need to setup an acct.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I'm also in favor of a video.
Sim
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