New proect! 1953 Hoffman Television Super Receiver Mark V Tv Phono Radio Console

[vortalexfan]

Originally Posted by Yamamaya42

have only found 3 really bad resistors, but replacing them has not helped.

new tubes on the way
6BA6 1st/2nd am/fm IF and AM RF amp, 6BE6. FM OSC and AM conv. and 12AT7 FM RF AMP/MIXER.
if this does not get the radio working, I will just give up on it. as the TV was the main goal anyway.

If I would of known you needed some tubes I had a whole ton of 6BE6 and 6BA6 tubes as well as a bunch of 12AT7 tubes that all test like brand new yet (they were pulled from radios that I was unable to get going electrically but the tubes were still good) that I could of sent you a couple of each for the cost of shipping.

But anyways it's good to hear you're making progress with this radio.

I'm curious is this the same unit as the one Shango has that he is planning on working on in one of his future videos that he picked up in one of his TV pick runs?

[Yamamaya42]

Originally Posted by vortalexfan

If I would of known you needed some tubes I had a whole ton of 6BE6 and 6BA6 tubes as well as a bunch of 12AT7 tubes that all test like brand new yet (they were pulled from radios that I was unable to get going electrically but the tubes were still good) that I could of sent you a couple of each for the cost of shipping.

But anyways it's good to hear you're making progress with this radio.

I'm curious is this the same unit as the one Shango has that he is planning on working on in one of his future videos that he picked up in one of his TV pick runs?

sort of, but 5 years newer, with a 21 rectangle CRT, but made very much the same way.

[vortalexfan]

Originally Posted by Yamamaya42

sort of, but 5 years newer, with a 21 rectangle CRT, but made very much the same way.

OK, I was wondering about that, because I know Hoffman was an L. A. area manufacturer that seems to come up a lot in Shango's videos (another brand is Packard-Bell.)

[Jeffhs]

Originally Posted by Yamamaya42

have only found 3 really bad resistors, but replacing them has not helped.

new tubes on the way
6BA6 1st/2nd am/fm IF and AM RF amp, 6BE6. FM OSC and AM conv. and 12AT7 FM RF AMP/MIXER.
if this does not get the radio working, I will just give up on it. as the TV was the main goal anyway.

Is the radio working at all, or is it completely silent? If it is still silent after you replace the tubes you mentioned, I would check one more thing before giving up: the antenna connections. If these are disconnected or the antenna itself has a poor or outright open connection, your set's radio will not work at all, unless you are in an extremely strong signal area, and even then you may receive only a small number of stations. However, as I said, the first thing I would do would be to replace the three tubes you mentioned, as one of them may be weak or burned out. If any of the tubes you mention are defective in any way, you will either lose reception altogether or, if you hear anything, the signals will be very weak and noisy.

The radio in your Hoffman console should work very well, as the set was made in 1953, when not every city or town in the United States had local radio. Because of this, the sets had to be, and generally were, built for DX (reception of radio stations located some distance from the set's own location); this is why I say the radio in your console should, indeed must, work almost exceedingly well. In radio's very early days, the first sets were crystal sets with no amplification, so a very good antenna had to be used in order to get any reception at all. My first crystal set was hooked up to a 50-foot (more or less) long-wire antenna and received one local station located only a mile or two from where I lived at the time. However, I will never forget one night right after that station signed off for the night (it was a 500-watt daytime-only operation in a Cleveland suburb). I heard the local station sign off, then, to my dumbfounded surprise, I heard, very weakly, one or two local Cleveland stations in my headphones, one on top of the other (crystal radios are anything but selective).

[Yamamaya42]

Originally Posted by Jeffhs

Is the radio working at all, or is it completely silent?

completely silent.

both AM/FM

though slight hiss heard in FM, and when I tap the FM aunt terminals with something metal I get some kind of sound change.
tubes will be shipped snail mail mon/tue

[Jeffhs]

Originally Posted by Yamamaya42

completely silent.

both AM/FM

though slight hiss heard in FM, and when I tap the FM aunt terminals with something metal I get some kind of sound change.
tubes will be shipped snail mail mon/tue

That's good to know. I hope the new tubes get your Hoffman console's radio working again. If you can hear a slight hiss on FM, and you hear a slight change in that hiss when you touch the FM antenna terminals with a screwdriver or anything metal, all is not lost.

As I said, the new tubes should restore normal operation; if not, I don't know what else could be causing the problem. If there is no reception on both AM and FM, and new tubes do not get things going again, the problem must be in a part of the radio (other than tubes) which is common to both bands. I've been away from electronics too long (I had to give up my workshop when I moved from my former home to an apartment over 20 years ago) to be able to offer any further advice.

[vortalexfan]

Now the interesting thing is that I had a late 1940s vintage Westinghouse AM/FM Radio (a Model H-1821) that had a similar problem (no signal being picked up on either AM or FM) and I tried replacing several of the IF, RF and Audio tubes and even recapped and replaced all out of tolerance resistors and nothing fixed the issue, (I suspected that either one of the oscillator coils was bad or a bad antenna coil or maybe a bad IF can, but either way the radio was a total loss so I just salvaged the cord, pilot light and the tubes from the unit and scrapped it out, because if it was one of the IF cans or coils that was bad there was no way I would of found replacements for it as they were an oddball style of coils and cans.)

So with that in mind, and I hope that isn't what's wrong with your radio, but I would check the antenna or oscillator coils first and then if those check out then check the IF cans.

[Yamamaya42]

I'm still tending to think (hope) that it's a symptom of bad/weak tubes, all I can tell is that all the general voltages in the RF/IF area are there, but 50-55 volts higher than shown in the schematic.

If there was an open coil, there would be a missing plate bias, and all are there.
YES, the power supply has been changed due to the burn out, but I doubt that is the problem here.

300acv tap is being used, rather than 340v original, 1kv 1a silicon diodes rather than 5U4GB, first resistor in voltage divider changed from 500 to 600 ohms.

Amp section working flawlessly.
Even if I lower the main input to 70-75v, it makes no difference, Amp still happy, raidio quiet.
USPS says the ordered ones will be here in 2 days, will just have to keep fingers crossed.

Shame that I don't have easy access to a tester here,

[Electronic M]

In my experience RF/IF stages usually work better with excessive B+... About 5 years ago I got a trio of Sherwood tuners and one had one had a dead power transformer...I cobbled up a replacement but had ~50V too much B+ IIRC. It worked NOTICABLY better than the stock one.

[Yamamaya42]

Radio is alive!

https://www.youtube.com/watch?v=lje6Zb-WLv8

it WAS bad tubes!

namely the 6BE6.

It's quiet easy to push this little amp into clipping, not that I expect much from this hoffman made thing.
15 amps max.
It was not made to do very much

[Yamamaya42]

turntable now working.

was in pieces when i got it.

https://i.imgur.com/oQpJZgJ.jpg
https://i.imgur.com/l6wpJFo.jpg

the Shure Crystal cartridge in there was quite deaf, and i was NOT about to pay $100+ for a replacement for something that would be rarely used, this is just for looks, eye candy, so I got a CHEAP ceramic one ($10) and glued it in place!
https://www.youtube.com/watch?v=XZ4fX4Akdxo

[Yamamaya42]

https://www.youtube.com/watch?v=L6A0UguQTV4

All done, for now, radio (FM) & Phonograph working, AM still a bit weird, but that will almost never be used.
Sensitivity and accuracy of the FM is impressive for something this old.
However, as mentioned the performance of the 6V6 outputs is rather sad, but not surprising, seeing that in this configuration it's rated at 14W max @ like 5-10% distortion? And that I'm sure would be with tubes in excellent condition, which I do NOT have.
May be able to get SOME improvement by a NOS phase inverter (6SN7GT) & MP6V6, but most likely not worth it at this point for something that will be used mostly for TV sound.

Speaking of which, the next phase of all this is trying to clear up the video on the TV by IF alignment, no easy task, with just a voltmeter and a digital RFfrequency generator.

[Yamamaya42]

https://youtu.be/DMDs4f7zv9M

all together now!

[Yamamaya42]

As you can see, the set is pretty close to done, just a few minor things to do to it left.

I decided NOT to attempt an IF alignment on it after seeing the video was cleaner on CH4 than 3, and may even be better on higher channels, and chances were 50/50 of making it worse/better w/o correct equipment, as sweep marker generators for 45.75mhz are sill around, but 25.5mhz is almost, but not quite unobtainium.
The picture it produces now is pretty good for it's age, just some slight ringing seen in it, not TOO bad, if I wanted it any better at this point, I'd have to make up a video amp and boost the composite input to 5v P2P, and right now, it's not really worth it.

All that remains to be done now is to replace the asbestos DEATH sheet heat shield that was above the AMP/Radio unit, that thing puts out a HECK of a lot of heat, perhaps add a fan to it, add a secondary grounding wire between all the chassis units, and add a master power strip, I don't like how it was all originally daisy chained.

[vortalexfan]

Originally Posted by Yamamaya42

As you can see, the set is pretty close to done, just a few minor things to do to it left.

I decided NOT to attempt an IF alignment on it after seeing the video was cleaner on CH4 than 3, and may even be better on higher channels, and chances were 50/50 of making it worse/better w/o correct equipment, as sweep marker generators for 45.75mhz are sill around, but 25.5mhz is almost, but not quite unobtainium.
The picture it produces now is pretty good for it's age, just some slight ringing seen in it, not TOO bad, if I wanted it any better at this point, I'd have to make up a video amp and boost the composite input to 5v P2P, and right now, it's not really worth it.

All that remains to be done now is to replace the asbestos DEATH sheet heat shield that was above the AMP/Radio unit, that thing puts out a HECK of a lot of heat, perhaps add a fan to it, add a secondary grounding wire between all the chassis units, and add a master power strip, I don't like how it was all originally daisy chained.

On most of the radios I've worked on that had a sheet of asbestos in the cabinet as a heat shield, I usually just leave it be if its still in good shape (which is usually the case 95% of the time on the radios I've worked on) because they say that as long as the asbestos isn't disturbed or flaking then you're ok to leave it in place, otherwise if its been disturbed, damaged or otherwise compromised then that's when you have to remove it.

As for disposal I don't know what the rules are for where you live, but where I live usually you just take the asbestos put it into a plastic bag and seal it up like you would any other garbage bag and then throw it in the trash dumpster, or take it to your local sanitary landfill to dispose of it.

Anyways I'm glad you got it up and running.