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 Post subject: Flakey DC on a TS-505d Military VTVM
PostPosted: Jul Sun 26, 2009 1:58 am 
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Joined: Apr Fri 24, 2009 2:14 am
Posts: 540
Location: Charleston SC .. USA
Hi... I have a TS-505d VTVM that I have beem working on.. I have replaced all tubes with Tested NOS ones.. I have replaced the 5 meg DC probe resistor.. What I have is when you switch to the DC range the Meter deflects slowly and its hard to zero .. and when you test a DC voltage the needle slowly moves up scale toward the voltage reading.. but dosn't read correctly...
I can email schematic or http://www.bunkerofdoom.com/lit/ts505/ts505d.html
Can someone help?

Mike


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 Post subject:
PostPosted: Jul Sun 26, 2009 2:17 am 
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Joined: Apr Sat 11, 2009 4:15 am
Posts: 1214
Location: Portland OR, grid square CN-85
Hi there Mike---
Sounds like perhaps the calibration is off ? Have you let the meter burn in ? If not, power it up on any setting, and then let it run for awhile, I let mine run overnight before attempting any calibration procedures, and that worked out fine. The 505 is a great meter to have, I have the 505D, the lid is long gone, but the meter is intact, just gotta replace a couple of probes, but that is about it. If this does not help at all, you may have a burned out or shorted resistor. I have heard of this happening if the meter has been overloaded, but I have never had any trouble with it at all. If these things are running and taken care of, they will literally run forever, sort of. Soooo, we gotta get yours out of Sick Bay and back into the field ! If you can get me a more detailed account of what is and is not happening, I can help more, I have access to a TS-505A manual, and I used it to get mine going, hopefully we can do the same for you. :D

Best Regards---
Tom


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 Post subject:
PostPosted: Jul Sun 26, 2009 2:37 am 
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Joined: Jul Tue 21, 2009 1:38 pm
Posts: 991
Location: SW WA state
Hi Mike....

I tried opening the links, but couldn't get the information to download.
Off hand, tubes are a small part of the equation. I clean all switches with a non-lubricating contact cleaner, let the switches dry, and then treat with De-Oxit. Being Frugal, I bought the applicator with 100% active ingredient that I apply a drop at a time to the switch in question.
I've had a lot of problems with test equipment and radios that drove me buggy, but disappeared when I cleaned the switches.
Even though the 505 claims not to have electrolytics, I would still suspect bad caps.
Check to see if it has any paper foils. If so replace them all! Leakage through them might account for the drift you're seeing.
Also, resistors don't age well. I've had fits with Gonset Communicators (30-50% out of tolerance), my RCA WT-110-A (all power resistors FUBARed and about 30% of the other out of tolerance), etc., etc.
Clean the contacts, check all the components, and slog on...
Best of Luck!

-Tom


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 Post subject:
PostPosted: Jul Sun 26, 2009 5:21 am 
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Joined: Apr Sat 11, 2009 4:15 am
Posts: 1214
Location: Portland OR, grid square CN-85
Hi there fellows---
I have the schematic for the 505 that is from the Bunker of Doom, I may have to go and dig here..... The 505 has NO electrolytics inside, and it has a spendy sealed electrolytic in it, for the filter cap most likely. If you want, I can send the schematic, send me an email at: signalcorpsoperator@gmail.com if you want it. The 505 is made to such specs that it will last a lifetime if properly fed and watered. They are very handy to have around, and are very rugged, another plus ! Mine has lost the lid and the accessories that went in it somehow, so I gotta find a new lid for it. But that is the easy part, I pulled the circuit boards, contact cleanered the tube sockets, and then let it burn in overnight. I then was able to calibrate it using a Weston standard cell, with a voltage of 1.02 volts. The meter calibrate to ONE NEEDLE WIDTH OVER 1 VOLT !!! 'Bout as accurate as you can get with an analog ! :D Let us know here Mike, I am glad to help.

Regards---
Tom


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 Post subject:
PostPosted: Jul Mon 27, 2009 12:23 am 
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Joined: Apr Fri 24, 2009 2:14 am
Posts: 540
Location: Charleston SC .. USA
Here is where I am... The Ohms ranges work properly.. only the AC/DC ranges are flakey.. when you switch to either AC/DC ranges the needle moves very slowly in any direction.. weather you are trying to zero or measuring voltage.. and dosn't read correctly... The schematic is very confusing trying to follow through the various switches.. On the link I posted with the Schematic.. if you right click and save as target you can down load it...

Any Help appreciated...

Mike


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 Post subject:
PostPosted: Jul Mon 27, 2009 6:17 am 
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Joined: Apr Sat 11, 2009 4:15 am
Posts: 1214
Location: Portland OR, grid square CN-85
Hi Mike---
OK, if I were you, I would measure the resistance of R17, I think that it is 200K or something. Anyway, if that is out of whack, try replacing it and see what that would do. Also you should try the Zero pot, see if that is in spec, when you measure the pot, use an analog meter, that way you can see the needle gently swing along. If the meter needle jerks, you may have a shot control. I will go and read up on the manual, we'll see what we have here...... I think that somewhere in the meter there must be an open resistor, it is doubtful that a cap has gone out, the ones in there are usually very high quality micas. The only one that might have possibly gone out could be the filter cap, but if that is out, your meter would not be a happy camper at all. Let us know here......

Regards---
Tom


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 Post subject:
PostPosted: Jul Mon 27, 2009 2:12 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 116
Location: caseyville il
Hello Everyone
Signalcorpsoperator i think you have him on the right track.
Were you stationed at Fort Gordon ?
I was there from 1962 to 1965 i was in electronic divices repair.
I taught the repair of the 25f and several other instruments
not the ts505 i do have one and love it.
Time Radio
George Kirk


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 Post subject: Re: Flakey DC on a TS-505d Military VTVM
PostPosted: Nov Thu 07, 2019 6:14 pm 
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Joined: Apr Wed 13, 2016 1:23 am
Posts: 145
Location: Independence, MO
Greetings forum,
I too have a TS-505 D/U VTVM I can't zero. Replaced all caps except .5 uF in power supply, replaced R17 a bit out and I still can't get it to zero. Ohms works great, AC seems to work but I have to get DC working first. My problem is, when I try to course zero I can get it to zero but it will drift up slowly. I also tried burning it in but the next morning the needle was pegged to the far right. Cleaned rusty switches( yes it has seen some water) Deox-it re clean, inspect??? Any thoughts out there??? Any help would be greatly appreciated.
Thank you in advance for you consideration.

Jim-----Did I not POST this corectly?? I have this on the bench now. Please someone help. checked all the pots only one was out--100k--tests 92k :lol:


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 Post subject: Re: Flakey DC on a TS-505d Military VTVM
PostPosted: Nov Mon 11, 2019 6:04 am 
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Joined: Aug Sat 17, 2019 5:35 pm
Posts: 18
Do you have the manual? I just had a quick look through the troubleshooting section of the 505A/U manual. It has solutions for drifting needle issues on different DC scales. I recollect having a similar issue several years ago with my meter. I think it was a defective tube in my case. If you dont have the manuals search for the following sites in Google:

Bunkerofdoom

Radionerds

Sincerely
Steve


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 Post subject: Re: Flakey DC on a TS-505d Military VTVM
PostPosted: Nov Mon 11, 2019 8:33 pm 
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Joined: Apr Wed 13, 2016 1:23 am
Posts: 145
Location: Independence, MO
Chappy, Thank you. Yes, I have the compete tech. service and repair manual from radio nerds. It's about 300+ pages. However, nothing they tell me works. I now suspect a bad tube. Must be the 6AU6 amplifier tubes. I have replaced the selenium rectifier temporarily and it seems to work better. Although the unit did not test bad. Now when I switch modes, +DC-+- DC and back again---the needle is pegged to the left. The only solution I have found is to turn the course zero all the way counter clockwise, then slowly tweek it clockwise until zero is achieved.

Thank you again.

Jim


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 Post subject: Re: Flakey DC on a TS-505d Military VTVM
PostPosted: Nov Tue 12, 2019 11:51 pm 
Member

Joined: Apr Wed 13, 2016 1:23 am
Posts: 145
Location: Independence, MO
Greetings all,
I have side lined my TS-505 D/U VTVM due to the mica-mold .5uF capacitors in the power supply were bad. I don't know where to get them. Anyone out there know??? I also found a flaky 6AU6 tube---it would test fine but if you leave the test going ---pushing P4 then you can see a gradual decrease in gm.

Jim


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 Post subject: Re: Flakey DC on a TS-505d Military VTVM
PostPosted: Nov Wed 13, 2019 7:02 am 
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Joined: Aug Sat 17, 2019 5:35 pm
Posts: 18
I am having issues with my 505B/U as well. The wire wound zeroing control has a broken winding, and the AC cal pot is flakey. I have replaced the zeroing control but still need to clean or replace th AC zero pot. After calibration I get an accurate measurements of DC voltages with the first measurement. If I then disconnect the leads and short them together I find that the needle now offsets itself a few divisions from the zero mark. Subsequent measurements now overread the voltage by a few divisions. If I then readjust the zero control, I can get the needle to return to the correct zero needle placement. Hmmm.

Im going to test my tubes for gas, or inconsistent gm like you found with one of your tubes.

With regards to your two oil filled power supply caps, C8 & C9, how did you determine that they were bad? Measured value, leakage, or ESR? I have several used caps in this style that are used pulls from an old military flight simulator. Ill see if I have the correct values for you, and check to see if they are functional.

Another alternative could be radial orange drop caps 0.47 or 0.5V rated at 630V and available at the following sites:
Justradios.com, or

Tubesandmore.com

Although they wont look authentic, they might give satisfactory performance.

Sincerely
Steve


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 Post subject: Re: Flakey DC on a TS-505d Military VTVM
PostPosted: Nov Wed 13, 2019 4:38 pm 
Member

Joined: Apr Wed 13, 2016 1:23 am
Posts: 145
Location: Independence, MO
Chappy, I tested the caps on my Knite 670 cap checker and they seem to leak--or something. So I replaced them with 2 electrolytic s @1uF 400v. Zero almost made it, that was before I changed the 6AU6. Zero still drifted up. Then I reconnected the 2 .5uF and needle moves rapidly to the right. So I determined they were bad. Thank you for the information I had not thought of that.

Jim


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