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 Post subject: Re: Crosley 9-408 [RCA 630TS clone]
PostPosted: Mar Thu 08, 2018 6:04 pm 

Joined: May Thu 14, 2015 4:15 pm
Posts: 679
Location: Dallas, TX
If you send the meter to a calibration company it will cost more that buying a new meter.
It may not be necessary you might get close enough by measuring a fresh battery cell.
The way I run my railroad is to have one new name brand factory calibrated meter that I use
as a standard. Maybe someone near to you can help you out.

"Excellent!" I cried. "Elementary," said he. - Sherlock Holmes

 Post subject: Re: Crosley 9-408 [RCA 630TS clone]
PostPosted: Mar Thu 08, 2018 8:19 pm 
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Joined: Mar Sun 01, 2009 10:27 pm
Posts: 4399
Location: Ann Arbor, MI
stuben wrote:
I will have to ship this to someone to have it calibrated and am wondering if anyone here might be able to recommend someone in the northeast who might be able to help me out.

The Heathkit VTVM that I have has a small dot on the meter face just above the highest mark. The manual says to buy a new carbon-zinc battery and adjust the meter so that the needle points to that dot. I just measured a new alkaline battery with my DVM and it measures 1.601 volts. So you could use an alkaline battery as a voltage standard to adjust your meter.

I have a high precision voltage standard that I got from the place where I worked. It is good to 6 decimal places. But you don't need anything like that to adjust a VTVM.


 Post subject: Re: Crosley 9-408 [RCA 630TS clone]
PostPosted: Mar Fri 09, 2018 5:28 pm 

Joined: Jun Thu 25, 2015 3:21 am
Posts: 1227
if you have a tube tester i would check the tubes in your vtvm. not only for emitions but if it is a dual tube you want both halves balanced. balanced means you get the same reading for both halves of the tube. to work on vacuum tube electronics you will really need a good tube tester.

you have the ac/ohms dc and ground lead for your vtvm. a high voltage probe is something used to measure voltages higher than the maximum voltage allowed by your meter. a rf probe would be used to take measurements in rf and if circuits. if you can i would try to get both these probes for your vtvm.

to check calibration on your vtvm you can get away with using the ac plug for the ac range a battery for the dc range and several persision resistors for the ohm meter range. if you have a dvm which you said earlier i think compare the readings to that. also a vom of not less than 20000 ohms per volt can be used to compare readings. try to find the manual for your vtvm and it should have a calabration proceedure listed. for proper calabration the most important thing is the tube in the bridge circuit is balanced.

you use a vtvm the same way you would use a vom or dvm to make measurements.

if you dont have a tube tester you really should get one. hickok is the best in my opinion. they also cost an arm and a leg. mutual conductance tester is the best but a emitions tester will due and is less expensive. no one tube tester will cover all tubes. make sure the tester you buy has the necessary sockets to test the tubes you will need to test. mine has sockets for the old 4pin 5pin 6pin 7 pin tubes found in early radios an octal socket loctal socket 7 pin minature and 9 pin minature which will cover most if not all the tubes i need to test. if you work on newer equiptment you will need a tester that also will test magnoval novar and decal tubes as well as nuvistors. so what vintage tester you buy depends on what you want to use it for.

to work on tvs a good crt tester is indispensible in my opinion. also a b@k television analyst is very helpfull. i own the 1075 television analyst.

for soldering to the chassis a 150 watt soldering gun and for soldering to a tube socket a 75 watt gun. anything less just wont cut it. a good desoldering bulb is also good to have but you can get away with solder wick.

a good condenser tester is also necessary.

for color tv work you will need a good dot bar generator.

an inductance meter will come in handy.

for doing alignment on televisions an oscilascope is necessary for some steps.

a sweap generator and marker generator also is necessary.

im sure im forgeting something but this will get you started.

 Post subject: Re: Crosley 9-408 [RCA 630TS clone]
PostPosted: Mar Wed 14, 2018 4:39 pm 

Joined: Oct Thu 23, 2014 5:15 pm
Posts: 69
Thanks thomas13202! Wow! That is a lot of gear to have to own and way beyond my budget. After re capping my RCA 8T241, which was very clean and all there I was rewarded with a set that works very well and I enjoy watching it. I guess I just got lucky. I do have a friend who went to electronics school that has an oscilloscope and lots of other gear and he knows someone local that collects old televisions so he may be able to help me out.

I'm still working on this Crosley 9-408 and decided to remove the transformer as the flux band needed to be re soldered and the light rust painted so that has been done. I am painting the chassis where it was rusted and removed the tuner, as I did not want any of that stuff getting inside the tuner then sandblasted with 220 aluminum oxide before painting to ensure a good bond to areas that were galvanized. While removing the tuner, there were two shielded wires one of which is green that not only had the shield soldered to the chassis but the green wire too. This did not seem right so I checked the wiring diagram in the Riders manual and it shows this wire should be soldered to pins 5&6 of valve #108, a 6AT6 the first audio amp, so maybe this was my problem. I also went ahead and ordered several new resistors from just radios to replace ones that had drifted out of spec. It will be a while before I get everything back together, but I will be making an update in a week or so.

Thanks again all!

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