Bose 4401 CD-4 Demodulator?

[Asklia]

Hi,
I'm also refreshing my Bose 4401 and I'd be interested in knowing the RCA sockets reference you have been installing, along with the Molex multiple pin connectors, if a male rhodium (golden aspect) plated exists. After 50 years, the nickel plated ones tend to suffer from corrosion.
Thanks !

I would have to search again, but I ordered both the Molex conncetors (gold plated) as well as the RCA sockets from Farnell.

 

[Asklia]

Very interesting article, thanks for the post!
I had never heard of the TDM-29C chip. Wow I've never seen a CD-4 circuit so simple. It must be an amazing chip. I wonder if it made its way into commercial equipment?

There's been a Compcor (Wireless World) & SWTP CD-4 kit so it's been done before. That gives the potential if you can't buy a perfectly working vintage CD-4 unit, build one. If you can find the right demod chips.

The TDM29 is >NOT< a single chip. Its a board like the TDM19 shown above. Probably with the same CD4-392 chips. It goes in this kit shown to a PCB connector; like in the Bose.

 

[Asklia]

I have a dead Bose 4401, of course its missing its demodulator... I was looking for a reference to a particular issue on demodulator crosstalk. Remembered a mention. II dug up someones scan of Audio Magazine November 1976. I actually bought this copy in paper. I had the entire PDF, but I've sliced out just the article. Its on Building Latest CD-4 Demodulator.

JVC created a TDM-29C and with outside help, supplied it as a kit to electronic enthusiasts. A fully assembled JVC TDM-29C card was included with a circuit board for a high gain phono preamp to match its latest CD-4 Demodulator. I've never seen mention of the TDM-29C. I thought to myself this thread might enjoy this PDF.

I hope you not dot discard your dead Bose. It can be repaired. Or sell it, eventually to me

 

[THM]

The TDM29 is >NOT< a single chip. Its a board like the TDM19 shown above. Probably with the same CD4-392 chips. It goes in this kit shown to a PCB connector; like in the Bose.

I would have to search again, but I ordered both the Molex conncetors (gold plated) as well as the RCA sockets from Farnell.

Thanks.
This is also where I searched, to no avail. According to the manufacturer the RCA sockets are now discontinued and they've become unobtainable from anywhere : Product – Lumberg
That's not very important since the nickel plated ones on my preamp are in rather good condition and it'll save me the hassle of desoldering 44 sockets.
As for the Molex connectors I'm still searching.

 

[Asklia]

To my last knowledge, they are available still in chrome version. By far better than nothing

And these ones here are for the Space and Image Composer:
https://www.lumberg.com/en/products/product/1571+01

 

[Asklia]

Here is a seller at ebay with a "slightly" overprised offer. At least four golden ones for 2 x Phono In.

https://www.ebay.de/itm/25512972286...D%3D|ampid:PL_CLK|clp:2047675&epid=5018855744

 

[Asklia]

by the way: "the hassle of desoldering 44 sockets" is not a simple task, since the Bose workers bent for each socket one or more of the legs.

 

[THM]

Here is a seller at ebay with a "slightly" overprised offer. At least four golden ones for 2 x Phono In.

https://www.ebay.de/itm/25512972286...D%3D|ampid:PL_CLK|clp:2047675&epid=5018855744

Ah ah ah ah

 

[THM]

To my last knowledge, they are available still in chrome version. By far better than nothing

And these ones here are for the Space and Image Composer:
https://www.lumberg.com/en/products/product/1571+01

Thanks. This ain't any better than the sockets I have on my preamp, which are in very good condition. I'll leave as it is.

 

[Asklia]

With a lot of work I succeded in galvanizing the three connector bars for the phono board. The problem (and big work) is removing the tin from the surface of the brass.

Although used for polishing brass, hot and concentrated citric acid does not work for removing the tin. And nitric acid attacks brass as well as it removes tin. But the reaction with tin is somewhat faster, so concentration of the acid (around 15%) and good timing does the job.

After that, manual polishing with sandpaper grain 7000 is necessary to get the brass shining (again). A lot of elbow grease is necessary

Commercial gold solution for chemical galvanization does the job afterwords at 90 °C.

 

[Owen Smith]

Galvanising specifically means zinc electroplating, at least in the UK. Whereas you've chemically plated it with gold, which isn't galvanising on two counts. I had to read your post several times to convince myself I hadn't missed something and this wasn't halfway to actually galvanising them.

 

[Asklia]

Oh, I am very sorry for this misunderstanding. Galvanizing in Germany and Switzerland is the name of the technique, not the material. I coated the surface indeed with Gold, not Zinc.

 

[Owen Smith]

Oh, I am very sorry for this misunderstanding. Galvanizing in Germany and Switzerland is the name of the technique, not the material. I coated the surface indeed with Gold, not Zinc.

Not a problem, the term is used (and spelled) differently in the two countries. Thanks for clarifying.

 

[Asklia]

Some more connectors done.



Before and after. Rule: Only shining surfaces will shine after the Gold bath. So really perfect cleaning and polishing is the secret.

 

[Asklia]

If anybody is interested in changing the sockets for these connectors:

MOLEX CONN RCPT 6P 0.156 GOLD EDGE MNT
Digi Key No.: PART: 23-0009483065-ND

Other pinouts as well available. With these new sockets, both sides have golden surface for the contact.

 

[THM]

If anybody is interested in changing the sockets for these connectors:

MOLEX CONN RCPT 6P 0.156 GOLD EDGE MNT
Digi Key No.: PART: 23-0009483065-ND

Other pinouts as well available. With these new sockets, both sides have golden surface for the contact.

Thanks, excellent

 

[Asklia]

By the way: I have read the specs of the "silver" colored Lumberg RCA connectors: Outside part Nickel, Inside part of the connector Tin. Whysoever.

 

[THM]

By the way: I have read the specs of the "silver" colored Lumberg RCA connectors: Outside part Nickel, Inside part of the connector Tin. Whysoever.

yeah, I had seen that, hence me keeping the original ones that can be cleaned and polished if one want to have shiny sockets.

 

[Asklia]

Wise. New ones would ave been the same, except the now unavailable golden ones.

 

[Asklia]

Some Impressions from the Alchemy and the results. Digikey delivered the Molex connectors for upside, downside and edge version. Since a 15-pin edge version in gold was not available, I re-used the old see-through plastic frame with the new golden spring plates of another pinout, as can be seen in the picture. Amazing, after half a century, there are still compatible or identical products available! Nevertheless, I did not find the vertical connecting bars. Therefore the "golden chemistry".