Packard Forum Index » Post-War (1946-54)

Just contacted people who sell radio parts here in UK. His reply was below , very confusing, do you know what he means?
?
The 6AV6 is a miniature double diode-triode valve (B7G base, all glass) used for detection,n AGC and AF amplification. It makes sense that such miniature valves would be used in a car radio, to save space - but the set is unlikely to function with just the one type of valve. At the very least I'd expect to see an AF output valve. There may be one or more 6AV6's in the set, though. You need the circuit data unless you can find a label somewhere on or in the radio with valve numbers and locations.
Regards
?
Tony

?
?
?

Apparently you asked about a single valve. He gave you the specs on that one but the radio has, depending on models, 5 or more. He is saying just the one won't do much if by itself or if something else is wrong. Here for example is instructions and a schematic for I think a 22nd series radio which has 7 plus a rectifier so 8 valves in total.

Attach file:

---

Size: 1,163.79 KB; Hits: 55

I think that there's been a misunderstanding here. When I referenced the 6AU6 in the earlier post, I was simply using that valve to illustrate that there shouldn't be any interchangeability issues between American valves and Euro valves. I'm not suggesting that your radio even has that valve in it.

If it's available in the UK, try to track down a Photofact Folder (produced by the Howard Sams, Co.) for your radio. It'll provide the schematic, parts list, and all the information you'll need to service your radio.

Sorry for the confusion.

Sent diagram to radio people. Reply below-:


Hi Gary
?
As best I can make out from the poor quality scan, your valve line-up is as follows, with possible alternatives in brackets:
2 off 7A7 (CV877)
2 off 7C5 output pentodes, working in push-pull . No substitutes made
1 off 7C4 rectifier (U149). This is a little odd as the valve has a different and larger base than the others, but it seems to be the correct one.
1 off 7B6 detector/LF amp, double diode triode type. (CV882)
1 off 7B8 (VT208)
1 off 7A4 phase-splitter (VT192)
?
You may have problems locating these valves in the UK. In the first instance I suggest that you telephone Geoff Davies on?01788 574774. Geoff deals in valves and other components. You can mention my name, if you wish. If he can't help, then do a Google search for valve suppliers. This could be a longish process and you may need to contact more than one in order to get a full set of valves.
Of course you could also post a wanted thread for them on the Vintage Radio Forum. You never know!
?
Hope this helps a little.
?
Regards
?
Tony

According to this siteradiomuseum.org/tubes/tube_7c5.html the 7C5 can be sub'd. No idea if that sub is still available though. Another site says a 7B5 will work as well. The rectifier or also the vibrator can be replaced with a modern solid state retrofit if that were needed.

As others have mentioned, valves are the least of the troubles when getting an old radio operational. The capacitors and anything with degraded insulation must be changed first. After that if a valve is needed, then if NOS & a sub is not available there is always used or possibly Russian.

One thing I have heard but not sure of is a slight difference in frequency standard between US and Europe. Someone with a direct American import can say if that is true and if something has to be adjusted.

Antique Electronic Supply:
7A7 $4.40
7C5 $7.95
7C4 N/A
7B6 $4.00
7B8 $3.00
7A4 N/A

I'm sure the two that aren't sold here are available readily elsewhere. Again, like I've mentioned and HH56 has also stated, the valves probably aren't the problem.

There are millions of original, NOS valves available at reasonable prices. When transistor radios came in every radio shop was stuck with thousands of valves and they never go bad. They are made of glass and the inside is under a vacuum so they will last for 100 years or more in dry storage.

A friend of mine has 25000 of them in his basement. All gathered up from defunct radio repair shops within a radius of 50 miles.

They are all substantially the same. By that I mean a 6AV6 is a 6AV6 no matter who makes it. The old ones are usually superior to new Chinese made valves. Russian valves are sometimes very good, sometimes not so good.

The best valves are old Mil Spec (military specification) army surplus. They were made to a higher standard than ordinary valves.

The valves themselves are not usually the problem. A tech with the right tester can test them and tell at once if they are up to spec or not.

The most common fault in old car radios, is the vibrator. It changes DC to AC. Sometimes they can be repaired, or a NOS replacement secured. It is also possible to make an all electronic substitute which lasts much longer and has the additional benefit of eliminating the hum.

Next up is the capacitors. The old ones were made of wax paper tinfoil cardboard and wax. They had an average life span of 10 to 20 years. They can be replaced with modern Mylar capacitors which have a much longer life.

A good valve radio tech can bring your radio back to life and make it work like new. In fact much better than any new AM radio. It is also possible to add an FM receiver, or MP3 player to play through the original tube amp circuit.

Here is a supplier in Canada who can furnish a copy of the original schematic as well as capacitors. I have dealt with him before and found him reliable.

justradios.com/

Hi HH.56

I saw Gary's Topic "Steering wheels" after which I realised he was over here and residing in Cambridge - - - we are now in touch and he's in contact with my friend George who has a stock of Packard parts - including a fully restored 22nd Series radio.

I've not submitted a blog on my restoration, pity I know but time just seems to slip by !! - I'm getting to the tail end and she is currently in the trim shop having a headlining and other interior bits and pieces fitted.

Best regards Michael

Cheers Michael, now in contact with George. When i get my project, hopefully next year, at wishes of both seller and me, i will know for sure just what i need. The radio sounds perfect. Great contact to have.