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 Post subject: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Nov Tue 13, 2007 5:37 pm 
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Joined: May Sat 26, 2007 8:07 pm
Posts: 52
Location: Norway
I have a couple of old Hickoks, and wonder;
Would it be a problem to update/modify an older tester to a later spec? (change signal voltage from 5V to 2,5V, and use later chart)
I have (and had) some Hickok that measure low on the 5V, and thinking of 3 ways to correct: add winding(not always practical), add another trafo for the 5V winding only, or reduce to the later spec. 2,5V, wich seems more interesting & practical..?

Arne K


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 Post subject:
PostPosted: Nov Fri 16, 2007 5:58 pm 
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Joined: May Sat 26, 2007 8:07 pm
Posts: 52
Location: Norway
:?: Is there any reason that this should not work?
- or have I overlooked anything?
As far as I can see, all other voltages are the same...

Arne K


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 Post subject:
PostPosted: Nov Fri 16, 2007 8:40 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
It's not practical. The A versions use more sensitive meters, and different values of resistors. I'm at work now, but can check the meter ratings when I get home.


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 Post subject:
PostPosted: Nov Fri 16, 2007 8:57 pm 
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Joined: May Sat 26, 2007 8:07 pm
Posts: 52
Location: Norway
:o You are right about meters: 533: 1,4mA / 80 ohm, 533A: 500uA / 233 ohm.

Arne K


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 Post subject:
PostPosted: Nov Fri 16, 2007 11:06 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
I've read about other owners having low 5V windings too. I believe that Hickok compensated for it elsewhere in the circuit, and shipped the instruments anyway.


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Aug Tue 26, 2014 1:47 am 
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Joined: Jun Wed 04, 2014 2:50 pm
Posts: 64
I have a 533A silver plate. I calibration company said that I have a low 5 volt signal winding of 4.6 and my testers transformer is failing so he could not calibrate. I thought the 533A had a 2.5 signal voltage?


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Aug Tue 26, 2014 2:23 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
Maybe it uses 5V for the lowest Gm range? I don't own one.


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Aug Tue 26, 2014 2:24 am 
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Joined: Aug Tue 13, 2013 3:18 am
Posts: 1089
Location: Milwaukee, Wisconsin
I have a 533A, and my understanding is if you only press P4, you get the 5v. But if you press P1 and P4, you get the 2.5v. If you look through the charts, you'll see which tubes it tells you to test using both buttons. I've always understood that to mean only certain tubes benefited from the smaller voltage.

Edit: I think I was half wrong. I looked back at the calibration instructions, and that only applies to the screen voltage and the plate is either 5 o 2.5 based on if it's A or not. At least I think. I just read the dang thing and my mind blanked out by the time I got back up to my computer!


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Aug Tue 26, 2014 1:12 pm 
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Joined: Jun Wed 04, 2014 2:50 pm
Posts: 64
Alan I am referring to your post from recent past that talks about " I've read about other owners having low 5V windings too. I believe that Hickok compensated for it elsewhere in the circuit, and shipped the instruments anyway. Maybe this what is possibly happening in my 533A where the service tech from Scherrer says my 5 volt signal winding is low 4.6 v. ( bad Transformer?)


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Aug Tue 26, 2014 7:25 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25381
Location: Pocasset, Cape Cod, MA
Well if the winding is 4.6V now, it always has been. There's no way to "lose turns." I expect you could sneak a couple more in, through some gap in the windings, but whether the unexpected capacitance to other windings would be a problem, I couldn't say. There's not much to lose by trying it. Of course if you have to ship the tester to someone else to find out if it works, the expense mounts, not to mention the risk of damage.


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Aug Tue 26, 2014 8:07 pm 
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Joined: Jun Wed 04, 2014 2:50 pm
Posts: 64
Alan Is this the case you were referring too where the 5 volt secondary was low from the factory, Do this winding prevent the tester from being calibrated? Transformer don't weaken? they either work or fail (short out) ?
I'm not sure what is valid after the report from this service guy?
Does any one know of a QUALIFIED service place I can send my hickok 533A to get tested ?
or should i believe this other guy that the tester has a bad transformer and its not worth restoring


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 Post subject: Re: Hickok 533 -> 533A (or similar) upgrade?
PostPosted: Apr Sat 04, 2020 12:57 am 
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Joined: Oct Mon 10, 2011 3:03 am
Posts: 19
Bkisker wrote:
I have a 533A silver plate. I calibration company said that I have a low 5 volt signal winding of 4.6 and my testers transformer is failing so he could not calibrate. I thought the 533A had a 2.5 signal voltage?


I know this is an ancient thread, but that's what the OP stated. He has a 533 that uses 5.0v for the grid signal voltage - too high for tubes like the 12AX7. He wanted to know if he can modify it to use 2.5v like the 533A. I say that can be done because I have one - although it came from the factory like that! Has all the features of a 533A EXCEPT the meter, and it reads a calibration 6L6 on the money, as well as 12AX7(A) tubes. I've included some photos.

Richard


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