Vintage electronics thread

[bruce1]

I have never seen anything like that. The cabinet is rougher than I would want to tackle but I know some who would if the piece was sufficiently rare or they just wanted to. I may have tubes if you have a dead one. I scrapped a Philco some years ago and I think I still have the tubes.

I found this site with much info re Philco radios

PHILCORADIO.COM - The Philco Radio Gallery - 1948 (June 1947)

This model is similar if not the same
The Model 48-1201 "Bing Crosby Special" was the 1948 version of the extremely popular 1946-47 Model 46-1201. 5 tubes, AM only.

 

[bruce1]

This site has a diagram and more pictures

48-1201 (48 1201) * Radio Philco, Philadelphia

 

[Gumby]

If you are going to tackle it, I would scrap the veneer and replace it with new. here is a site for veneer
Walnut Veneer

 

[Nodak]

I have never seen anything like that. The cabinet is rougher than I would want to tackle but I know some who would if the piece was sufficiently rare or they just wanted to. I may have tubes if you have a dead one. I scrapped a Philco some years ago and I think I still have the tubes.

I found this site with much info re Philco radios

PHILCORADIO.COM - The Philco Radio Gallery - 1948 (June 1947)

This model is similar if not the same
The Model 48-1201 "Bing Crosby Special" was the 1948 version of the extremely popular 1946-47 Model 46-1201. 5 tubes, AM only.

I am a member of the Philco Phorum and looked for info there. I have the tubes the unit uses but I think it's just beyond fixing.

 

[ERD50]

I am a member of the Philco Phorum and looked for info there. I have the tubes the unit uses but I think it's just beyond fixing.

But that format is so unique (at least to me), that maybe it is worth just 'fixing up', even if not totally restored? I'll guess it isn't worth any great value restored, so is there much to lose if some of the repairs are not totally authentic? I think it would be neat just to get the case looking nice, and being able to open and close it to show off how it worked, even if it wasn't functional. It's not like you are really going to play a 78 on there very often. heh - I was recently thinking about the FM radios that went low enough in the band to pick up some TV audio (this feature was mentioned in a few modern portable players), but then I realized those audio channels are gone, it's all digital now. Not that's obsolescence!

Like Gumby says, re-veneering isn't really that tough. I'm not that skilled with cabinetry, but I've done some veneer projects that turned out pretty well with nothing more than razor knives and contact cement (or even 'iron on' with some glues), fine sandpaper and shellac (or your dye/stain and finish of choice). They're about 15 YO with no bubbles or loose seams or anything.

Question for you guys - what's the life expectancy of big old, tabbed aluminium can electrolytic caps (3000uF 50V)? I'm working on a classic Fender Rhodes piano (circa 1975) for the school Jazz Band, the power supply in it is acting up. These caps appear to be OK (I've got to verify that a bit more), but I was thinking of maybe just replacing them anyhow. About 5 years ago, I rebuilt the 'stereo' tremolo circuit in it - one of the two light bulbs that drives the photocells was burnt out and replacements were high priced plus shipping. I'm no purist, there are LEDS in there now.

-ERD50

 

[Nodak]

As it happens a friend of mine is going to take the radio and see if he can do anything with the cabinet as I know nothing about wood working. Between the two of us we might get it working again; I even have some 78s to play on it.

 

[Telly]

Ran across this very rough Philco radio phonograph and don't know if it's worth trying to fix.

Loktal tubes! I ran across few Philco's years ago. Those Loktal tubes were a Philco invention, supposedly less likely to vibrate loose in auto applications, I guess. You could do yourself some harm trying to unplug those suckers when they were old, it's like they welded themselves in.

 

[Telly]

Question for you guys - what's the life expectancy of big old, tabbed aluminium can electrolytic caps (3000uF 50V)? I'm working on a classic Fender Rhodes piano (circa 1975) for the school Jazz Band, the power supply in it is acting up. These caps appear to be OK (I've got to verify that a bit more), but I was thinking of maybe just replacing them anyhow. About 5 years ago, I rebuilt the 'stereo' tremolo circuit in it - one of the two light bulbs that drives the photocells was burnt out and replacements were high priced plus shipping. I'm no purist, there are LEDS in there now.

-ERD50

Many years ago I learned that aluminum electrolytics that sat around unpowered for a long time could be salvaged, if done carefully. This assumes no leakage of electrolyte. When unpowered, the aluminum oxide film (the insulator between the plates) slowly breaks down. Would see this when firing up old shortwave radios, etc.

The leakage current would be high, power transformer would run hot after 15 mins or so, and a lot of 120 Hz. hum due to ripple current on B+ due to leaky caps. Would turn it off by 10 - 15 minutes, allow to cool, power up again later in the day. By running them just for intermittent periods, you could re-form the aluminum oxide layer. After that, would work great and transformer would not overheat. Took a bunch of cycles to do it, can run longer each time.

But in the industrial world, aluminum cap life in the 1970's was affected by the use of Freon, Freon TE was one of them, as a flux remover after wave soldering. The freon could make it past a lot of the rubber tire can end seals, and attack the electrolyte. Eventually, they made better sealing caps that could take freon tank immersion. I remember some early fixes, like cap vendors charging extra for "sealed" caps. On axial-leaded parts, they extended the mylar anti-short overwrap around the can outwards on the positive end, and poured in a layer of epoxy. This added roughly 1/4" onto the overall length.

 

[Nodak]

Loktal tubes! I ran across few Philco's years ago. Those Loktal tubes were a Philco invention, supposedly less likely to vibrate loose in auto applications, I guess. You could do yourself some harm trying to unplug those suckers when they were old, it's like they welded themselves in.

I am familiar with Loktal tubes, I put myself through computer school in the late 60s buying old radios from the Salvation Army, fixing them up and selling them. I cut myself a few times working on those old Loktals. It was a surprise to me at the time just how long tubes would last; 80% of the time an old radio could be brought back to good condition just by re-capping. Never had to replace that many tubes.

 

[ERD50]

The leakage current would be high, power transformer would run hot after 15 mins or so, and a lot of 120 Hz. hum due to ripple current on B+ due to leaky caps. Would turn it off by 10 - 15 minutes, allow to cool, power up again later in the day. By running them just for intermittent periods, you could re-form the aluminum oxide layer. After that, would work great and transformer would not overheat. Took a bunch of cycles to do it, can run longer each time.

Thanks Telly! That loosened up some brain cells from over 30 years ago. One early project I had was to pull some huge Telco power supplies out of inventory, and run through a cycle of 'reforming' the big, huge, honkin' electrolytic caps in them, and then tagging them with the date the process was performed. We bolted big, huge, honkin' acrylic shields to them before we powered them up from a safe(?) distance, as the leakage could be enough to cause them to blow (though the safety vents should make that a relatively unexciting event).

I don't have a scope handy, so haven't been able to check ripple, but no signs of overheating. Though the problem is the next stage regulator is way low, and it's possible that ripple could throw it off (back biasing things if the downstream caps are holding a charge and the B+ dips below that). My darn cheap digital multi-meters do not seem to be capable of measuring ripple - the DC on the AC throws them off - guess I can add a decoupling network, but I really need a scope. Might use an o'scope program and my laptop with a 100:1 divider on the mic input.

-ERD50

 

[ls99]

Mighty quiet lately.

Here is a puzzler for the afficionados. What is the device in the photo?

Hint: it was used in early Earthquake research. Both photos are the of the same device.

 

[NW-Bound]

I don't have a scope handy ... I really need a scope...

Then darn it, start looking on eBay. One can get a nice working Tektronix scope for around $100, solid-state and with bandwidth of more than 100MHz too.

PS. I wouldn't get an old tube type Tek scope to restore. Of course you can do that, but get a working solid-state one first.

 

[Nodak]

View attachment 11187View attachment 11188Mighty quiet lately.

Here is a puzzler for the afficionados. What is the device in the photo?

Hint: it was used in early Earthquake research. Both photos are the of the same device.

The only old Rubicon stuff I've ever seen was a galvanometer. don't know what else they made.

 

[ls99]

Quick solution Nodak. It is a galvanometer, with a tiny mirror attached to the rotor.

The output of a Wood Anderson Long Period seismometer was connected to the galvanometer.

It was used in concert with a slit light source as a noiseless amplifier. The light source and the photosensitive paper on a rotating drum was 15 feet from the galvanometer. Thus amplifying the varying signal of the seismometer.

All of which was on top of concrete pier poured on bedrock. This particular unit was used atop the Palisades rock formation just north of Alpine NJ. Taken out of service around 1980. Photosensitive paper (about 2'x4') got to be way too expensive. Saved this one from the junk yard. many others were tossed. I use it as a paperweight etc.

 

[Nodak]

An interesting modification for the galvanometer, it never would have occurred to me that they were ever used that way.

 

[NW-Bound]

Although I grew up playing with vacuum tubes, I do not see myself going back to that any time soon. Well, maybe when I fully retire and have more time. Right now, antique electronics to me means individual transistors, dual-gate MOSFETs, ICs that are in DIP packages, TTL chips, Z80 and 68000 microprocessors, etc... These 30-yr old ICs take tremendous board areas and are awfully power hungry compared to SMD devices now, hence are antique to me.

I remember a Tektronix spectrum analyzer from my early career, about 1975, that almost took two people to move it. It actually had two handles.

I still have in my garage a venerable HP-141t spectrum analyzer which weights perhaps 50lbs. No tubes in that granddaddy, except for the CRT. All the circuits are solid-state, but the weight is because of the tremendous shielding that the thing has. For accessories, I have all the 3 plugins: HP8553 (1KHz-110MHz), HP8554 (100KHz-1250MHz), HP8555A (10MHz-18GHz). The IF is of course the HP8552B. I also have the HP8445B Preselector.

The above setup can still fetch some money, but no way I would want to sell it. Yes, even if I have a modern, lighter analyzer with a built-in tracking generator. That beauty and another piece of equipment, a lab grade signal generator, together cost me $50K when I bought them a few years ago. These are of course nowhere near top-of-the-line. For that, a top-notch best-money-can-buy spectrum analyzer with phase noise so low it brings tears to your eyes cost $99,500 back then.

PS. No, my memory was failing me. The analyzer was $25K and the signal generator was $15K for a total of $40K, not $50K.

 

[NW-Bound]

I just now went looking on eBay, and saw nothing other than non-working Tek scopes that the sellers still want way too much money for.

Admittedly, the last time I looked was a few years ago, and I could swear I saw many good deals then. Was I imagining it? Where have all these good used Tek scopes and HP analyzers gone? Did they all die and go to electronic heaven, and the remaining survivors now fetch higher prices, if one could be found?

 

[stevenst]

NW-bound: I started my career with the 8555A. Great instrument. I remember when we took delivery of the then-new 8565. It was immediately dubbed the 'Star Wars analyzer' because it had a cool red LED readout of the (approximate) frequency. Oooh.

Steve

 

[ERD50]

An interesting modification for the galvanometer, it never would have occurred to me that they were ever used that way.

Yes, interesting stuff. I googled and just found galvanometers.

I just now went looking on eBay, and saw nothing other than non-working Tek scopes that the sellers still want way too much money for.

I'm trying to stay in a de-accumulating phase, otherwise I'd probably just by the scope. But when a laptop has 99% of what I would need for what I might do, I'd rather just try to use that instead of buy another piece of 'stuff'.

I loaded xoscope on my linux machine. It's not too bad, but the mic/line inputs on my laptop are AC coupled, so that makes it less usefull than I would like for general troubleshooting, where I want to see AC and DC levels. Hmmm, I have an ADC I bought for converting my vinyl, that might have DC coupled inputs on the line jacks, and I think I can get xoscope to read from the USB channel. I'll give that a try. I think I have a 10x probe around somewhere.

-ERD50

 

[NW-Bound]

I'm trying to stay in a de-accumulating phase, otherwise I'd probably just buy the scope.

Even if I were going to live full-time in a small motor home, I would be sure to find room for my 3 scopes, 2 spectrum analyzers, and 2 signal generators (all Tek and HP lab quality equipments). Of course there were other little things like power supplies. Oh, and of course my junk boxes of parts... And my 5 desktop PCs (dual core and quad core). I guess I will leave behind the single cores that I still keep.

A geek can de-cumulate or whatever, but he's still got to remember what is important to him, ya know?

Maybe I would need to move up to a class A motor home, you think?

... I think I can get xoscope to read from the USB channel. I'll give that a try. I think I have a 10x probe around somewhere.

Is that probe enough attenuation to probe around high-voltage circuits with a low-voltage ADC?


PS. You are trying to de-cumulate, yet you are also trying to restore old and bulky antique electronics? I say you need the scope!

 

[ERD50]

PS. You are trying to de-cumulate, yet you are also trying to restore old and bulky antique electronics? I say you need the scope!

But the stuff I fixed/rebuilt wasn't mine (it's the schools), so it's outta here!

Is that probe enough attenuation to probe around high-voltage circuits with a low-voltage ADC?

Well, the line input of an audio DAC should take +/- 2V or so. So a 10:1 probe only gets me to 20 volts - I'd need to build another little divider in there for anything other than low voltage stuff.

-ERD50

 

[NW-Bound]

But the stuff I fixed/rebuilt wasn't mine (it's the schools), so it's outta here!

OK. I am different. Whatever I touch, I become attached to. So, at this point, I am very very careful not to get anything new. I have so much to play with already, I do not want to accumulate anymore.

 

[bruce1]

I still have in my garage a venerable HP-141t spectrum analyzer which weights perhaps 50lbs. No tubes in that granddaddy, except for the CRT. All the circuits are solid-state, but the weight is because of the tremendous shielding that the thing has. For accessories, I have all the 3 plugins: HP8553 (1KHz-110MHz), HP8554 (100KHz-1250MHz), HP8555A (10MHz-18GHz). The IF is of course the HP8552B. I also have the HP8445B Preselector.

snip

I used these as well. We just had the HP8554 plug in. Remember the cameras with the polaroid back that were use to record the screen. I feel old now.

 

[DRiP Guy]

I just now went looking on eBay, and saw nothing other than non-working Tek scopes that the sellers still want way too much money for.

Admittedly, the last time I looked was a few years ago, and I could swear I saw many good deals then. Was I imagining it? Where have all these good used Tek scopes and HP analyzers gone? Did they all die and go to electronic heaven, and the remaining survivors now fetch higher prices, if one could be found?

I wonder if our grandkids will collect these as 'vintage' someday:

ARM DSO Nano - Pocket-Sized Digital Oscilloscope - eBay (item 200470598507 end time Mar-05-11 08:33:18 PST)

 

[NW-Bound]

If this thing lasts that long!

Damn! That's nice and cheap. At 1Msps, it is only good for audio work, and is not going to replace my 200MHz scope any time soon. But that looks perfect for people restoring audio tube equipment.

Maybe I will get one just to play with!