So far I have had no success jump starting either of the two original 4 pin vibrators that I have. I have both of them open and the points are not stuck on either of them, nothing looks or smells burned and using my meter it seems that I have no open circuits.
I've been through the archive and looked at all the previous material posted on this subject and tried the suggestions I found there. I have watched some vids. on Youtube produced by knowlegable people and while very informative I still would like to know why these units won't function just for my own satisfaction.
The batterys I have tried are a brand new 6 volt Optima and the 12 volt model in one of my vehicles. My tubes light up and the display lights work so I know the problem lies at least so far in the vibrator.
Any thoughts or suggestions would be welcome.
Thanks,
Anthony #15293
When removed, you should read come continuity between 3 of the vibrator pins. If not, you may have
oxidized over contacts from its age. Easiest solution is get a solid state replacement vibrator. It might
be possible to polish up the contacts and get it running. Someday I'd like to devise an electrical way to
break thru the oxide. Bruce Roe
Anthony,
The vacuum tubes filaments are feed via the low voltage side 6V; the vibrator is part of the high voltage circuit.
Attached is the radio diagram for the 7253207, which should be the one you have.
You may need to disconnect one leg of resistor #27 the 220 ohm to validate the primary side of the power transformer #51 for continuity, and also to check continuity on this resistor.
With the vibrator out, and a 6V supply to the radio, turn the switch “on†check the voltage at both ends of the vibrator socket, one should be ground the other two should read 6V.
These should give you a high level starting point in trouble shooting. You can also check the following site for more details on the vibrator power supple functions.
http://radioremembered.org/vpwrsup.htm
Good luck..!
Thank you Bruce and J,
I will use your information and see what I can accomplish. When you think about a radio we normally take their function for granted since they usually work; but what with the science and physics involved in creating one in the first place it really seems somewhat of a miracle.
Anthony #15293
When I was young vibrator failure was the primary reason for radio failure. They were usually installed in a location that made them easy to replace such as on the bottom of the radio. I would consider a solid state vibrator now if you can tolerate the lack of the hum produced by the vibrator.
Anthony,Check out the answer on how to start a vibrator in this section from November, 30 2012 reply #9 Doug tells how to burn thru the tarnish on the points and get it working. good luck. Marty
Thanks Gary and Martin; I did use Doug's technique but to no avail. I think the points are just to far gone even though they were not stuck together. If they were supposed to look like a set of ignition points when new, these were in tough shape and far from what they were when new. This is probably why they will not operate. Filing them was not recommended and burnishing them in this condition would have been impossible.
Went ahead and ordered a new unit through Tayman Electrical in Cal. and this is a solid state, MOSFET design which has no need of the condensor used by the original vibrator. Will see how it works when I get it installed.
Anthony #15293
So I replaced the old vibrator with the new solid state mosfet model. I still have no sound and the only tubes I know for sure are at least lighting up are the two 6V6 GT units at the bottom of the chassis. These come on when I hit the power switch. Could the OZ4 rectifier tube be an issue as I have seen many negative rermarks regarding them on radio forums. I have no way to test this old one and I see they are relatively cheap and plentiful online. I was going to swap a GE 6X5 GT for the old OZ4 but upon removing the 6X5 from my parts radio I noticed it has a burned through filament. I haven't blown any fuses with this unit and the one it came with was still good.
Clearly, it had a bad vibrator and the string up inside the push button selector was broken to have probably sidelined it in the first place.
Any further thoughts?
Thanks.
Anthony #15293
Anthony,
You need to check the rest of the tubes for 6V at the filament side (or heater as noted on the diagram), there could be an open/lose wire going to the rest of the tubes.
If you have a voltmeter verify there is voltage going to the rest of the tubes at the corresponding pins for the filament (heater), one side of the filament should be positive and the other side would be negative/ground.
If you are not familiar with the tubes pin out, check this site
6SR7 -http://www.r-type.org/exhib/aaa0055.htm
6SK7 - http://www.r-type.org/exhib/aag0065.htm
6SA7 - http://www.r-type.org/exhib/aaq0021.htm
Good luck..!
Hey, just turn on the radio for a few minutes; tubes not burned out will heat up. OZ4s failed
all the time; next thing to swap after the vibrator. A quick check for a couple hundred VDC on
the 0Z4 output (or the pate pin on any other tube, can be pulled out) will tell if the supply is
working. Or noise from the speaker when turning the volume.
Really, note that those big polarized cap(s) by the 0Z4 are not failing and killing the supply.
I may have worked out a sure fire way to burn through oxidized vibrator contacts. NOT a
fix for burned out contacts. Anyone got an oxidized vib to try it out on?
Bruce Roe
Anthony,if you haven't got the radio to work yet I found a place in upstate N.Y. that had mine fixed in a week. Send me a message if you want their info. Marty.
Marty, thanks for the offer but I put the word out locally here with some of my car buddys and was referred to someone I went to Jr. High with and whose father was an TV and electronics tech. The son apparently followed him into the field. Also, a friend who is involved in Ham radio gave me a name of one of his friends who is local and also into Ham. He is apparently a retired electronics guy in his seventies who can get this unit back on track. I will talk with both of them and see who wants to work on it.
I got my new OZ4 tube and installed it to no avail. I know you guys are right and that I have an open somewhere in the loop. Hopefully now that I have a couple of experts to turn to, I can get this squared away. Will let you know what the final outcome is.
Anthony #15293
So, I finally got to the bottom of my radio issues thanks to a fantastic company located in Salt Lake City by the name of Interwest Electronics Corporation.
The new vibrator I had installed was defective, they replaced the 65R7 tube, and for good measure reconed the speaker. It plays perfectly now.
I highly recommend them and you can locate them online. They have been in business since the twenties or thirties, I believe.
Anthony #15293
Quote from: A. Amman #15293So, I finally got to the bottom of my radio issues
thanks to a fantastic company located in Salt Lake City by the name of Interwest
Electronics Corporation.
they replaced the 65R7 tube
Good to know; that is likely a 6SR7 tube. Bruce Roe
Quote from: bcroeI may have worked out a sure fire way to burn through oxidized
vibrator contacts. NOT a fix for burned out contacts. Anyone got an oxidized vib to try it out on?
Bruce Roe
It came up; a hardly used vibrator I bought in the 50s wouldn't run, because the contacts
had oxidized over. So I built this fixture to try and get past the oxide. This is NOT a fix for
burned out contacts.
The vibrator has a common pin, with a NC contact to one pin and a NO contact to another.
A coil is connected between the common and the NO; it attracts the armature, operates the
contacts, shorts itself out (the NO closes), releases, and a repeating cycle is energized. Even
if the contacts are both reading open, the coil resistance should be evident at the pins.
I connected common to + power, a couple 2A bulbs (1157 both filaments) to the contacts.
The NC bulb connects to - power. The NO contact bulb goes to a transistor, which conducts
to - power. Even if the contact are not making, I can drive the transistor with a square wave
to make the armature vibrate. The idea is, if I leave it vibrating for some hours, the oxide may
be worn through; this will be very evident when the bulbs begin to light up. Now the vibrator
will be able to run normally again, so the transistor may be shorted out (with a switch), and
the vibrator will run on its own. The real test, is turn it off and back on; it should be able to
restart on its own.
I used a pulse generator to drive the transistor. Tuning around between 60 and 150 HZ, it
was easy to tell by feel where the vibrator would operate. The pulse gen could be replaced
by a simple C555 chip with a frequency knob. So far I have brought back a vibrator known
to be lightly used; another that was probably burned didn't recover. 6V and 12V are just a
matter of changing the power supply; keeping at the high end should help.
I have another method involving burning through with high voltage, but its harder to set
up. Bruce Roe