Gotta' Watch Those Repair Guys - Printable Version
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Gotta' Watch Those Repair Guys - Phlogiston - 03-05-2017
Working on a Philco 84.
It had been "fixed" before. I always wonder if the repair - no matter how messy - was successful.
So the oscillator would not run. Everything looked good. Hay, wait a minute. The gimmick cap had been unwound and run to the ground (-10V not the chassis). I have to believe that the "repairman" saw a wire with a loose end and decided to connect it to the nearest terminal.
So I know that this repair had been ultimately unsuccessful.
Works as good as an 84 can - now.
RE: Gotta' Watch Those Repair Guys - Ron Ramirez - 03-05-2017
I've encountered some previous "repairs" on radios that looked downright scary at times.
RE: Gotta' Watch Those Repair Guys - Arran - 03-06-2017
Speaking of a model 84, I bought a model 84 from a fellow collector, but it wasn't the same 84 that Russ was working on, this was a Canadian model 84 from 1950, looks like a 50-524. Anyhow this guy decided to replace the filter caps in it, with, I guess, whatever he had rolling around in his junk drawer. One cap was mounted under the chassis, where it should be, even though it was a 450 volt cap. The other was an axial cap, another 450 volt unit, mounted to the side of the bracket on the back of the speaker, with a wire twist tied around the body, it was connected electrically to the under side of the chassis with a pair of wires fished through a hole, and the connections at the cap itself were bare. Neither of these electrolytics were new, or if there were they were new old stock, and they didn't even match brand wise. Also for some strange reason, he had replaced a mica cap with a .047 uf, I think it was a 47 mmf on the schematic, it was a coupling cap I think so not as critical, still it was off by a factor of 1000s.
Regards
Arran
RE: Gotta' Watch Those Repair Guys - morzh - 03-06-2017
With some self-acclaimed "repairmen", "it is working now" is the criteria.
Which, to be honest, wasn't that bad when these were not valuable antiques. Guy saved some money by not paying to a trained tech and the radio worked.
RE: Gotta' Watch Those Repair Guys - John Bartley - 03-06-2017
Sometimes you have to both wonder how the sets worked when they came back, and also be glad for the education that all the troubleshooting provides.
My great-uncle had a late fourties Crosley-Mohawk (CDN) table top set in his spare bedroom for guests. When I inherited it I set about getting it rebuilt and found that it wouldn't work at all. (I always troubleshoot first and recap later). All the B+ voltages were screwy and ultimately I found that a wire was just plain missing, that wire being the one that tied the B- buss to the negative side of the PS circuit. To find it I had to trace every single wire and every single part in the set to find out what was missing, and that was only after I gave up testing voltages, and scoping signals and not getting anywhere. Once I installed that tiny little bit of wire that set sprang to life as if by magic!! I lost a lot of my hair to that set .... pure frustration! I always wondered how my uncle got that set back from the shop .....
RE: Gotta' Watch Those Repair Guys - gregb - 03-06-2017
The one error I have run into a number of times now and the most recent was on my Philco model 17. The filter cap on the negative bias supply, the one that has positive tied to ground was installed backwards with the negative to ground. I have seen this mistake at least half a dozen times or more now.
Gregb
RE: Gotta' Watch Those Repair Guys - morzh - 03-06-2017
Yeah it is kinda counter-intuitive. Especially if the person who restores/repairs it is new to tubes and has been dealing mostly with solid state or is learning on the fly. From the solid state the depleted mode FETs are the only ones that use negative bias and their usage since has dwindled.
RE: Gotta' Watch Those Repair Guys - gregb - 03-06-2017
Another interesting one I just saw on a 39-30 was a long ago tech moved the negative bias supply connection for the 41 output tube from before the resistor network and attached it straight to ground. The result for me was an open primary on the output transformer. I wonder what the guy was thinking when he did this. The radio hum level must have increased and I would think there may have been audio distortion. Wonder how he explained this to the owner at the time.
Gregb
RE: Gotta' Watch Those Repair Guys - morzh - 03-06-2017
Greg
Could it be that the resistor was open (happens a lot with the vitreous enameled wirewounds) and so the replacement would be costlier than tolerating a bit of hum?
RE: Gotta' Watch Those Repair Guys - gregb - 03-06-2017
This one used two carbon comps and both were fine and in tolerance. I reconnected the wire where it should be and installed a new output transformer and all was good.
Gregb
RE: Gotta' Watch Those Repair Guys - TV MAN - 03-09-2017
Most all of us here are "Restorers" and work as such, taking care to use quality replacement parts, install them carefully, check and address possible future problems, check alignment, trying our best to make our restoration the best that we can. We take the time. Repairman was a whole different world. There were very good ones with a good reputation and others that were shady, inexperienced and incompetent. Often either the tech was pushed for output (ask me how I know this), dishonest, or just trying to make a living. Maybe he worked for an appliance business where repair was secondary, and he was to 'condemn' some of the older or more difficult to repair units in favor of selling a new unit.
If he was an independent, the more sets he could repair in a day, the more money he made, so long as it would run past his warranty period. He knew if it came back after that time, there would be another repair job. Also, if he is short on capitol, he may not stock many parts, and to order parts was time consuming and costly, all while the customer is breathing down his neck. I am sure some just read a book or two and started. Seems on repairs, you either have it or you don't. You would be surprised how many of my fellow techs (currently) are parts changers - not techs. They change parts until the unit works again, rather than paying attention and diagnosing the problem before attempting a repair. Then you have the dishonest repairman that would charge for new parts when using discounted, used parts, or charging for parts and services not even performed! That always burned me up!
Then, there is the "customer". They often want something for nothing and are impatient. So, if he can make it work again by soldering in an on hand part, clipping out a bad part or jumping something that will 'make it work' again, he has a completed paid service call and a customer off his back. Some customers are almost impossible to please. There are a lot of sets that are looked at, or a repair attempted, and if it appears to be a time consuming diagnoses and repair, he closes it up as 'not repairable' and moves on to easier jobs that he can make money on. Remember, most of these guys were in it to make a living, not a hobby like most of us. Yea, it is an aggravation when we see a hacked set, but also remember most of those old sets were "played out", used up before they were replaced, unlike what we often do today - which is upgrade. On the good, most of these old sets were owned by depression era people who never threw anything away.
Just my 2 cents
