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I'm a sucker for old, beat up, and obsolete 500 series plug-in's. Latest project is this Type 53/54G. It is very similar to the Type 53/54K recently restored but it has differential inputs while the Type 53/54K had a single input. I managed to talk the seller down in price and nicked it for $25 USD plus shipping. Luckily he was located in Staten Island (NYC) so it didn't have to travel far because the packaging wasn't the greatest. But it's in one piece.
As received. A mess of old sticker residue and asset tags.
"Goo-Gone" works wonders. Then a Simple Green wash down followed by ammonia based window cleaner to remove all residue. A vast improvement.
Follow up.....pictures and clean up of the interior.
An old gray beard with an attitude. I don't bite.....sometimes
What's wrong with this picture? Those vacuum tubes don't look right. Suspicions aroused. Suspicions confirmed. Some slimeball removed the original vacuum tubes and installed nearly worthless series string TV tubes to make the plug-in "look" complete. Do I think the seller did this? I want to give him the benefit of the doubt and say no, perhaps he got it this way. He did state he had to no way of testing the plug-in and was sold untested. So I'm not going to make a big stink about it. I have the right tubes in my stash. But for future reference just be aware that this could happen. The tubes that were installed are 4DE6, 4AV6, 4DT6A, 4BZ6, 19EA8, and 2 unmarked. All are nearly worthless series string TV tubes.
Fixed. 1 - 12AT7, 2 - 6AK5, 4 - 12AU6. Deoxit'ed the sockets and cleaned the chassis. Next on agenda is clean remaining controls, check supply lines for shorts, then plug into a mainframe for testing.
Last edited by MED6753 on Tue Mar 07, 2023 7:31 pm, edited 1 time in total.
An old gray beard with an attitude. I don't bite.....sometimes
WHOEVER did it, that's a total shitbag move. May all their filter caps short and their resistors drift way out of spec forevermore. Glad you had the proper firebottles on hand, Mike.
It seems underhand. I've once or twice bought equipment with dubious equivalent valves, or other codges, but never anything like that. Maybe those particular valves are sought after by the audio nutter community and that may explain it. It may be that the seller came by it and genuinely knows nothing about it, so the mischief was worked by someone else.
Just one of those things.
Occasionally it works the other way. About 15 years back I bought a Racal RA17 receiver, complete and in about the condition I expected, for a fair price. When I opened it up there was a bag of about 20 valves inside, about 75% tested good and all useful types (not TV rubbish with odd heater voltages).
I don't think the 6AK5 or the 12AU6 is much use to the audiophools. But both were used extensively in Tek equipment. The 12AT7 is definitely an audiophool favorite. It's in the same class as the sought after 12AU7 and 12AX7.
An old gray beard with an attitude. I don't bite.....sometimes
Cubdriver wrote: ↑Sat Mar 04, 2023 11:12 pm
Sadly, some of them are 'discovering' the 6DJ8, too.
-Pat
6DJ8's have been on their radar for a long time. The 6DJ8's in my stash are not attractive to the phool crowd. How so? Simply rub off the "Bugle Boy" decal on the tube. It comes off super easy.
An old gray beard with an attitude. I don't bite.....sometimes
MED6753 wrote: ↑Sun Mar 05, 2023 2:07 am
6DJ8's have been on their radar for a long time. The 6DJ8's in my stash are not attractive to the phool crowd. How so? Simply rub off the "Bugle Boy" decal on the tube. It comes off super easy.
But that makes the unquantifiable, unmeasurable magic they contain go away! They'll never work properly without it!
As Med says, 6DJ8/ECC88 has attracted the attention of audiophools for years.
E88CC/6922 is a closely related special quality valve, with gold pins (so it's assured to be remarkably musical, with a definite, but not overwhelming, presentation..........). It was designed as a computer valve. It had gold flashed pins, because with thousands of valves, bad pin contact was enough of a problem to be worth doing something about. Apart from that, what was special about it, was that it had cathodes designed to tolerate no cathode current for long periods, which will damage a normal cathode. It was never intended as an audio valve. They sell for ridiculous prices.
Despite the tube plug fiasco it appears that the rest of the plug-in is unmolested. Did a resistance check of supply voltages, pins 9 - 15 on the connector and no shorts observed.
First test on a Type 547. Initially trace was way off screen. Fiddling with DC Balance brought it back on screen but vertical centering is way off. Not surprising after many years idle. Combination of vertical centering adjust and DC Balance will fix that. Both inputs work and pass a very good 50kHz square wave. Noticed a slight offset when switching DC coupled to AC coupled on Input A but not B. That indicates a leaky DC block capacitor. It is a Tek made 0.1uf/600V 1% capacitor. Finding an exact replacement might be an issue and I may have to settle for a 10% replacement.
Since this plug-in is optimized for a lower B/W scope such as a Type 535A I'll continue the rest of the checkout/calibration/compensation on that scope. More to come.
An old gray beard with an attitude. I don't bite.....sometimes
Update. I should have checked my parts stash first. Scrap Type CA plug-in. Same P/N (285-556) DC blocking capacitors in newer sealed poly style rather than older paper. One measures 102.1nF and the other measures 102.5nF. Perfect.
An old gray beard with an attitude. I don't bite.....sometimes
Removed the leaky DC blocking capacitors and installed replacements. Forgot to get pictures. Here is the plug-in installed on the Type 535A. All adjustments readily accessible with the cover removed from the scope. The Vertical Position Range and DC Balance fell right into place without any fussing around. The vertical compensation for both inputs was surprisingly good even though the plug-in was completely re-tubed. Just some minor touch up. Even the Differential Balance came into place without any issues. So this plug-in is now complete. It started out ugly but finished off nicely.
An old gray beard with an attitude. I don't bite.....sometimes
As I stated at the beginning of this thread I'm a sucker for old 500 series plug-in's. Just bought this Type G plug-in which is the latest version of this differential plug-in. And it's from the same seller as before. These pictures are his as posted on Ebay. It clearly shows the correct vacuum tubes installed. If I receive it with garbage tubes plugged again I'll know the seller is a fraud and I'll have his ass nailed to the wall. I'll do the reveal when I receive it.
An old gray beard with an attitude. I don't bite.....sometimes
I received the Type G plug-in and guess what? We have vacuum tube fraud again. 5 of the 7 tubes are worthless series string TV tubes. All four 12AU6 were replaced with 2AU6. The 12AT7 was replaced with a 6LF8. I fired off a note to the seller and we'll see what he says. If he gives me shit I'll file a dispute with Ebay.
An old gray beard with an attitude. I don't bite.....sometimes
Correct vacuum tubes now installed except I'm short two 12AU6's. Ebay order submitted. The tube sockets were deoxit'ed and chassis cleaned. Tomorrow I'll clean up the front panel and deoxit all the switch decks.
Still haven't heard from the seller. Stay tuned.
An old gray beard with an attitude. I don't bite.....sometimes
MED6753 wrote: ↑Wed Sep 27, 2023 7:37 pm
I received the Type G plug-in and guess what? We have vacuum tube fraud again. 5 of the 7 tubes are worthless series string TV tubes. All four 12AU6 were replaced with 2AU6. The 12AT7 was replaced with a 6LF8. I fired off a note to the seller and we'll see what he says. If he gives me shit I'll file a dispute with Ebay.
MED6753 wrote: ↑Wed Sep 27, 2023 8:20 pm
Correct vacuum tubes now installed except I'm short two 12AU6's. Ebay order submitted. The tube sockets were deoxit'ed and chassis cleaned. Tomorrow I'll clean up the front panel and deoxit all the switch decks.
Still haven't heard from the seller. Stay tuned.
Just don't let him get away with it and give him hell!
The seller and I talked. He claims he takes these plug-in's on consignment from someone else. Knows nothing about them. Can't test them. Sold "as is". Doesn't know a $1 tube from a $50 tube. Is not trying to be deceitful. Yada, yada. Do I believe him? Maybe, but I'm still suspicious. Anyway, we agreed on a partial refund, which he already passed, that more than covers the cost of two 12AU6 tubes. So I'm happy and consider the matter closed. But I did suggest to him that he talk with his "supplier" because someone in that loop is ripping others off.
The seller is "themudlarks" and he is located in Staten island, NYC. I suggest avoiding him.
An old gray beard with an attitude. I don't bite.....sometimes
