Vintage Products

Re: Grand Prix 609 K Moderne questions...

yachadm — Tue, 29 Nov 2011 12:34:10 GMT

Aaron

Very strange that my BM3400 transformer also failed the same day!

Anyway, here is a link to Hammond who make output driver transformers for tube equipment (among many other types)

http://www.hammondmfg.com/5caud.htm

Perhaps there is a problem upstream of the transformers, which overstressed the windings....

Menahem

Re: Grand Prix 609 K Moderne questions...

Aarong — Sun, 27 Nov 2011 05:37:20 GMT

After the visit of Menahem at my home i'd the opportunity to see inside the 3400.

I helped to do the final tuning of the FM tuner.

Now let's go back to my 609K.

After recalibarting the FM tuner it's look very good. I replaced the ECC85 to E88CC and now i have 6db more gain.

The EF89 was changed to EF183. Now the FM receiver works very good.

Now the bad news... the 2 pushpull audio output transformers of the ECL86 are one anode side disconnected inside...so only one tube

is working in each amplifier.... (why?)

I replaced one of the xfmrs with one from my junk box that was inside not working Sansui 220 receiver.

So, at last the 609K is working, one channel only. i decided to live it as is for now, as i don't need stereo amplifier for this radio.

70 ohm 10W resistor inserted in the main line, to reduce the voltage inside. our main is 235Vac, and this radio is 220Vac.

for the last 3 days I enjoy very much to listen to this old FM radio, the AFC works great! and the sound is very good! (with external speaker).

I'l post in the future picturs and more data of the 609K.

Aaron

Re: Grand Prix 609 K Moderne questions...

yachadm — Wed, 23 Nov 2011 15:48:49 GMT

Great forum this! Great people.

I just spent yesterday evening with Aaron - a 2-hour drive from my place, and we had a great time at his workbench, doing some calibration together on vintage B&O equipment.

One meets the nicest people here, and it's great to have another very-capable fellow vintage B&O tech in Israel.

Menahem

Re: Grand Prix 609 K Moderne questions...

Dillen — Wed, 16 Nov 2011 12:00:29 GMT

Exactly ! A school example of tin whiskers.
Not hard to imagine how wrong this can go electrically.

Worth cleaning off the whole capacitor, I think.
A vacuum cleaner and a brush, I suppose, could do it.

Nice photos BTW.

Martin

Re: Grand Prix 609 K Moderne questions...

Aarong — Wed, 16 Nov 2011 10:39:57 GMT

Hi Martin,

very intersting! see the picturs below...

btw,the pictures in nasa site are of the same type of capacitor as mine...

Re: Grand Prix 609 K Moderne questions...

Dillen — Wed, 16 Nov 2011 09:31:45 GMT

Yes, of course, that would have been the cause !
Notes taken.

Martin

Re: Grand Prix 609 K Moderne questions...

tournedos — Wed, 16 Nov 2011 08:21:31 GMT

Dillen:
I know the phenomenon, it's called tin whiskers. Never saw it in a tuning capacitor myself though, but
I can't see why it wouldn't happen.

In retrospect, I think that was the fault in my Dirigent!

Funny that it would appear all the sudden, but I believe the receiver sat on a shelf for at least a decade right before I got it, so perhaps moving it around finally collapsed the whiskers and caused the short...

Re: Grand Prix 609 K Moderne questions...

Dillen — Wed, 16 Nov 2011 01:25:18 GMT

Well done !

I know the phenomenon, it's called tin whiskers. Never saw it in a tuning capacitor myself though, but
I can't see why it wouldn't happen.
Ultra thin hairs grow from tinned surfaces, sometimes seen as a single strand or two, other times as a close
woven carpet made of conducting metal strands.
The UK vintage radio forum did a larger research together with NASA on the subject and
NASA confirmed that it was indeed tin. It happens with silver, zinc and cadmium too in certain alloys.
It's a huge problem in certain germanium transistors (AF116/117 in particular) where the whiskers
grow from the inside surface of the metal housing, which is grounded in HF circuits, and eventually reaches
one or more junctions or leads inside the transistor, thereby disabling or even completely shorting the transistor.
The same thing happens regardless of the transistor being used or not. Even unused, old stock, devices can
have the fault. Tapping the transistor with a pencil or similar will sometimes see it burst into life but it won't last long.
In the Beomaster 900 models, a bracket holding an electrolytic capacitor is usually found completely
covered with tin whiskers.

More info and photos etc. on the subject
http://nepp.nasa.gov/whisker/photos/index.html

And of course, we would also like to see photos of your set.

Martin

Re: Grand Prix 609 K Moderne questions...

Aarong — Tue, 15 Nov 2011 19:16:05 GMT

Hi Martin.

Some good news here...

I found the problem in the FM tuner. it's a long story...

any way, I decided do disassemble the tuner from the radio, to make it easy to track the problem.

First, please note that the schematic you sent me is not as my tuner ! there is some variations.

Second, i found that one part of the variable capacitor have apprx. 47 ohm resistance to ground !!!

so when i looked with lupe inside the capacitor, I saw a very starnge fenommen inside the capacitor, that looks like a grass of metal hairs

that grew inside for about 50 years...

this metal "grass" was grew inside the frame of the capacitor, and made a short to ground,

that show 47 ohm between the ground and one stator of the capacitor, ! ! !

after a good cleaning with alcohool the variable capacitor is OK now !

I assemble back the capacitor, connected power to the tuner, and now It's WORKING !

later i will assemble back the tuner in the radio, I took a picture of the "short" in the capacitor before cleaning.

Re: Grand Prix 609 K Moderne questions...

Dillen — Mon, 14 Nov 2011 01:24:55 GMT

Aarong:

this tuner is very very uncommon in it's circuit. the oscillator/mixer is the right tube and the left tube is the RF amp. (correct?)

Quite common circuits for a B&O, really.
The "tubes" in the schematics is actually one tube. The ECC85 is a double-triode and to ease the reading of the schematics,
it has been divided into its two parts, indicated by the incomplete circle "glass envelope".
But yes, the left part in the schematics is the tuned RF amp, the right part is the mixer/osc.
It's a hard working tube.

Martin

Re: Grand Prix 609 K Moderne questions...

Aarong — Sun, 13 Nov 2011 16:58:58 GMT

Thanks!!! i opened the tuner cover. i'm testing the voltage on the tube, all looks ok.

this tuner is very very uncommon in it's circuit. the oscillator/mixer is the right tube and the left tube is the RF amp. (correct?)

few caps, around L102 and may be the Varicap of the AFC are suspects IMO. (i will continue on th enext day)

Re: Grand Prix 609 K Moderne questions...

Dillen — Sun, 13 Nov 2011 15:43:34 GMT

OK, we're back at the local osc. then.
It's merely a handful of components or two, the ECC85 tube being the only
active part.

Martin

Re: Grand Prix 609 K Moderne questions...

Aarong — Sun, 13 Nov 2011 14:11:02 GMT

No the FM tuner is not working yet. the test was done by injecting 10.7MHz FM signal from RF generator to the output of the tuner.,

so all the IF link can be checked and calibrated again. this is my general work with old FM radio's.

Re: Grand Prix 609 K Moderne questions...

Dillen — Sun, 13 Nov 2011 12:33:17 GMT

Aarong:

Regarding the FM noise, please note that low signal level station will be heard with low volume... if this is normal working of the FM radio.

Does this mean, that you actually have a station albeit weak ?
If that is the case, check the AGC line and voltages around the IF amplifiers.

Martin

Re: Grand Prix 609 K Moderne questions...

Aarong — Sun, 13 Nov 2011 10:31:00 GMT

The E88CC was replaced in my Balupunkt Sultan FM radio, that i restored few weeks ago.

I remember that the sensitivity of the radio was increased after changeing the original ECC85.

as noted , I didn't noticed any suspected components yet.

I see that I need the manual...(any help?)

i will try later this evening to continue my work.

Regarding the FM noise, please note that low signal level station will be heard with low volume... if this is normal working of the FM radio.

Today, all FM radio's works with Hi gain IF with limiter, on the IF chain, that give constant audio level, not dependent on the level of the

antenna signal, more or less...