[volt-nuts] Fluke 332B
kc9ieq at yahoo.com
Mon Feb 20 15:36:01 EST 2017
Very interesting, very curious to hear your conclusion!
My thought would be to replace these with standard value 5% resistors having good temp co, as calibration should surely make up for any subpar values-- my thinking is that temp drift would be a more major consideration for overall stability. If this is a false assumption of would certainly like to learn why. Perhaps the old Allen Bradley carbon comps were special in this regard, but the data sheet I've seen for currently available comp resistors had a horrible temperature coefficient-- much worse than the "better" film resistors available today. I stock the Vishay PR02 metal films for rebuilding old tube stuff, which have a temp comp of +/- 250ppm/K. There are much more stable options out there, but I chose this line because of the 500V rating and dark red/brown color which blends into an old chassis more so than tan or bright blue.
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-------- Original message --------From: Jerry Hancock <jerry at hanler.com> Date: 2/20/17 2:19 PM (GMT-06:00) To: kc9ieq <kc9ieq at yahoo.com>, Discussion of precise voltage measurement <volt-nuts at febo.com> Subject: Re: [volt-nuts] Fluke 332B
I have a D model but I would thin Dr. Frank would be able to address the difference D to B.
I recently went thru a Dial a Source DAS-46 finding so many (most) of the carbon comp resistors had changed value +30%. But, and this is the important ‘But’, the typical 1% metal film resistors don’t have good tempco. So I wonder if replacing these 40yr old resistors was a good idea. Yes, they have drifted higher, but since they all drifted up by the same percentage, the circuit still worked. I bought most of the high value from Mouser using Vishay as the default unless I couldn’t get them for some reason. I am running a test of the stability over 36,750 seconds (has to do with 10K samples with the 3457A in NPLC 100 taking about 3.675 seconds per) to see if the stability is better now vs with the carbon comp. Not that I would swap them back in, just curious.
> On Feb 20, 2017, at 12:01 PM, kc9ieq via volt-nuts <volt-nuts at febo.com> wrote:
> Thanks John and Jerry for the replies.
> After a visual inspection and noting one questionable looking capacitor, (breached seal), I've systematically gone through and checked every single electrolytic capacitor in the unit for C and ESR. No fewer than NINE have been identified as definitely defective- A few of which have effectively failed open. Surprisingly, most of these are Sprague 30D and TVA series. There are also a dozen or so by Amperex/Phillips (some made in Mexico), and three by Mepco/Electra. The three large 125uF 450V can capacitors are Mallory, and reformed to full voltage with acceptable leakage current. Given the multiple defective capacitors found, I will be replacing all bur the three large can caps before attempting to power up again and troubleshoot further.
> I do wonder if anyone on list has personal experience with the 332B and 332D, and just exactly what makes the 332D one decade more accurate according to the spec? Although the ones checked so far are within tolerance, I am considering the replacement of all carbon comp resistors with more stable metal films. Perhaps this would be a bit overkill and not yield much in the ratio of effort:performance though?
> Sent from my SMRTphone
> -------- Original message --------From: Jerry Hancock <jerry at hanler.com> Date: 2/14/17 11:38 AM (GMT-06:00) To: Chris Farley <kc9ieq at yahoo.com>, Discussion of precise voltage measurement <volt-nuts at febo.com> Subject: Re: [volt-nuts] Fluke 332B
> Most likely the relay in the back left of the box is not opening because the switch that controls it (the power/standby/operate) switch is fouled. If that relays contacts were cleaner then the tripping voltage would be lower. I had this happen and heard later it is a common problem. There is a long shaft that could be misaligned from the front to the back where the switch wafers are located. If that gets misaligned, the switch doesn’t open the relay which keeps the outputs shorted. The don’t short to a very low resistance when they are dirty. With the unit turned off, measure and record the resistance across the output high and low terminals. Use ohms law to determine if this is your problem. The current trips at 50mA. If it is tripping at 3v, then your resistance would be about 60 ohms. Once you get it working, go back and clean that relay.
> The other common problem is having the vernier current limit set too low. In that case, just turn the current limit dial all the way clockwise. Note that there is also a voltage trip variable control on the voltage trip knob.
>> On Feb 14, 2017, at 8:59 AM, Chris Farley via volt-nuts <volt-nuts at febo.com> wrote:
>> Geetings all,
>> New to the list and to a sickly Fluke 332B which kicks out the over current protection at a mere 3 or so Volts output.
>> This is just one of my current projects, but first a question before wasting bandwidth.. I see the list archive page, but is there a secondary, or SEARCHABLE archive of this list anywhere to see what has already been said in the past about this unit?
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