My all tube mid sixties magnavox console has been working like champ for years now. All of a sudden the FM will crap out. Ths is one of the consoles where the AM and FM are housed in seperate locations and signal strength ismeasured by a green tube. The AM works fine but after about ten minutes the FM will simply stop broadcasting. The powr is still pumping to the FM side just no broadcast. What is going on?

Thanks

Pull the tubes in the FM section and have them tested. Sounds like you have a weak/bad tube. Check all of them. Check the AMP and the AM tubes also as a preventative measure. Write down the tube number and the value from the tester for each tube as a baseline.

What Model # of Console? Do you have pics of the Tuners and AMP?? Can we see them???

Loose or dirty tube sockets will also produce those intermittent results.

Bad Capacitors; may lead to tube shorting out and going poof

My all tube mid sixties magnavox console has been working like champ for years now. All of a sudden the FM will crap out. Ths is one of the consoles where the AM and FM are housed in seperate locations and signal strength ismeasured by a green tube. The AM works fine but after about ten minutes the FM will simply stop broadcasting. The powr is still pumping to the FM side just no broadcast. What is going on?

Thanks

With a gree ntube tuning eye, I 'd better that is closer to mid 50's. Just a guess on my part.

With a gree ntube tuning eye, I 'd better that is closer to mid 50's. Just a guess on my part.

How about we try late 1940s?

If this console is one of those I'm thinking of, the FM tuner is a seperate chassis hanging "upside down" above the main (AM tuner/amp) chassis. These can be identified by the "CR" number stamped on the chassis also. If it is one of those, try this...

The FM tuner used a 6SB7Y as a convertor, and they had difficulty keeping those oscillating. Monitor the grid voltage on the oscillator section and be sure it stays at least -10 volts. If it doesn't, the tube is ceasing oscillation. Alternately, you could try another 6SB7Y and see if this cures the trouble. Unfortunately, this was a problem with that particular tube, and you may have to try several before you find one that works in your rig.

I hope this helps.

Note that the OP said GREEN TUBE, NOT GREEN EYE TUBE. I wondering if his "GREEN TUBE" is an EM84A. Not so much an eye but a double ended bar that meets in the middle to indicate centered tune. Both my '65 fishers have this tube.

I don't ever recall seeing any Magnavox's with a green tube, unless his "STEREO" Indicator Lens is Green or it's like TV Engineer said. Another possibility.

My 64 and 67 Maggies both have a TUNE strength Meter, and my 69 and 70's all have a light with a Red Jewel lens.

Larry

follow up:

the serials indeed start with CR. i posted a while back and identified the model and whatnot. i could look on the back again and find out what it is but i am currently listening to the t/t sitting on top of the console. anyway i plugged in the console and turned on the FM tuner and watched the back. no tubes seemed out of the ordinary, but it konked out after about 5 mins or less. the AM "broadcast" works fine. what can i do as a layman. i have a tube tester, but thats about it. is there a way to fix it? i miss listening to friday night FM on my console. is there someone in the madison, WI area that is into these things? i'll gladly brew 5 gallons of thier favorite beer as compensation.

thanks AK!

So, did you wiggle the tubes to see if the FM would come back in?

So, did you wiggle the tubes to see if the FM would come back in?

no. i figured i'd shock myself to death!

Grab the GLASS part of the tube at the top with TWO FINGERS and keep the other hand IN YOUR POCKET, wiggle it. You shouldn't get shocked unless you have an exposed wire or your chassis is "HOT". Meaning it doesn't have a power transformer.

With it being late 40's Assume it is a "HOT" Chassis. Get a RUBBER SHEET (DRY Rubber Door mat works well). Stand on it. Keep one hand in your pocket. Take a insulated tool (screwdriver with heatshrink on it) and tap or move the tube back and forth. If the FM goes in and out then you need to clean the pins and socket. If it doesn't, pull the tube and have it tested or replace the tube with a backup. Do what TV Engineer said to do. This will entail putting the whole setup OUT of the cabinet on a bench and then testing pin voltages.

Larry

I can assure you that the radio being discussed here is NOT a hot chassis. Magnavox only made a VERY limited number of hi-fi [U]consoles[U] in the very late 1950's that used a hot chassis, so no worries there.

Each chassis uses a 6E5 tuning eye. These were quite popular with Magnavox in some of their highest end chassis until 1961.

The FM chassis should be populated with all metal tubes, with the exception of the RF amp, which I believe is a 6AG5.

Thanks TV Eng. I wasn't sure, so assumed by age it may be a HOT Chassis.

Damn. Learned something today.

Larry

I can assure you that the radio being discussed here is NOT a hot chassis. Magnavox only made a VERY limited number of hi-fi [U]consoles[U] in the very late 1950's that used a hot chassis, so no worries there.

Each chassis uses a 6E5 tuning eye. These were quite popular with Magnavox in some of their highest end chassis until 1961.

The FM chassis should be populated with all metal tubes, with the exception of the RF amp, which I believe is a 6AG5.

what do you mean by "all metal tubes"

what do you mean by "all metal tubes"

Just that - tubes with a metal jacket.

ok folks. thanks for the great insight. i did exactly what you suggested. the FM cut out at 1:19 roughly. i got in the back and wiggled tubes. first off the glass tube closest to the the face plate (the tube on the bottom of the last picture.) seems affixed with some kind of wire harness. like a cage. i wiggled it and the music did not go in and out but i got a lot of static. the glass tube closest to me did nothing when wiggled. anyway i appreciate all your help and enjoy my terrible pictures. there is something wrong with my camera.

http://picasaweb.google.com/markechaney/Radio#

Sounds like Dirty contacts. Lets rule out a number of remedies, or problems one by one. CLEANING the Oxidation from TUBE Pins, Tube Sockets, Switches, Pots, and contact sliders will alleviate a myriad of problems. Make sure the equipment is CLEAN and making as complete a contact on each point as possible so it won't mask another problem.

Pull the tuner and the amp out. Clean the tube sockets and tube pins with DE-OXIT. You spray a little on the pins and insert the tube in the socket and cycle it in and out a number of times. Then wipe off the tube pins, flush out the socket with De-Oxit, and spray some faderlube in the socket and the pins. Put the tubes back in and wait a couple hours for it to dry sufficiently.

Crank it up. If it problem DOESN'T repeat itself, call it a day. If it DOES then you have other problems......

Can you take a picture of the ID PLATE? and the Tube layout if there is one?

Larry

ok. so i removed the tubes today. the stereo model number is 156b. i took the tubes out today. the 6sg7 tube is rattling. the thing that drives me nuts is when i took into the local tube guy he refused to give me any unpaid help and told me my tubes were worth more than my unit. so local tube help is out of the question. i took pictures of the unit but i am venting at my friends right now. more pictures later. basically i'm not sure what is wrong but i have the tubes out. the lass tube looks good the one of the metal 6sg7 tube is rattling....grrrr

pics:

http://picasaweb.google.com/markechaney/LastImport02#

i am very familiar with this tuner. i have had three of them at one time. in regards to the problem that you are having, i can tell you that the tuner will need to be re-capped & the resistors checked. i have found on all three tuners like the one you have, several resistors that have opened. it also uses those crappy MicaMold capacitors, which do not survive the test of time & are leaky

i am very familiar with this tuner. i have had three of them at one time. in regards to the problem that you are having, i can tell you that the tuner will need to be re-capped & the resistors checked. i have found on all three tuners like the one you have, several resistors that have opened. it also uses those crappy MicaMold capacitors, which do not survive the test of time & are leaky


how can i get this done here in madison, wi? anyone? anyone?

6E5 is called as 'Magic Eye' in Japan.

6E5 is called Magic Eye in Japan. They are sold even today.