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Re: 8566B attenuator removal
Okay, done a bit more testing. As was suggested, I bypassed the internal variable attenuator with a fixed 10dB one and attempted calibration once again. It now calibrates fine.
I thought whilst I had the front panel off but still connected, I'd run a test of the attenuator using a spare spectrum analyzer I have. Methodology was simply to squirt RF in at the input and measure its actual level of attenuation vs its stated level of attenuation for each of the settings 0 through -70dB using the front panel to change the settings each time.
Got some quite interesting results.
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Setting (dB) ??????????????????????????????????? Actual attenuation (dB)
0????????????????????????????????????????????????????????????? -20
-10????????????????????????????????????????????????????????? -30
-20?????????????? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? -20
-30 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? -30
-40 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? -40
-50 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? -50
-60 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? -70
-70 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? -80! (with massive noise so presumably dirty contacts)
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Clearly the attenuator needs to be removed and inspected, so that's what I shall now do... ??????????????????
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HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
Hello All,
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As a possible opportunity to upgrade my? test bench's HP 333A, I recently obtained a HP 339A distortion analyzer of unknown heritage, but very late serial number.
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Physically, not in too bad shape, all things considered:?
- missing bottom feet (not unusual, I suspect - probably was rack mounted) - I would be interested in finding these, if anyone knows of a source (new or used)
- missing end cap for input knob, otherwise all knobs complete (and not broken!)
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- Cleaned up well, internal inspection didn't reveal any previous obvious "tinkering", looked clean. Powered up and went through basic testing (using internal oscillator), seemed to mostly work but with the following observations:
1) Output monitor completely dead (not too worried about this yet)
2) Using the internal oscillator (1V output), for frequencies below ~3.5 KHz, the Freq. Input LED (counter clockwise) illuminates. I can extinguish the LED by moving the frequency vernier knob off of the "calibrated" detent position. If I do this, then all of the lower frequencies are reported to be in the notch filter's range and autoset works under this condition, depending on the actual frequency the vernier knob has to be set anywhere from just off the detent to about 2 o'clock max. As frequencies go lower than 3.5 KHz, the vernier has to be turned more CW. I've tried various voltage output settings (3, 0.1, .03) and the above behavior doesn't change as far as I can determine. Reported distortion values seem reasonably close (if not in,) to spec.
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What I've done so far:
- carefully deoxit only the metal contacts on all wafer switches (yes this took a while)
- re-seated the one board in a connector
- re-seated all cable and connectors
- loosened, re-tighted all mounting screws
- supplied missing endcap for input knob (my HP8640B parts bin had exactly one knob with the right cap size & color - from the output attenuator's center variable control, I believe)
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I am going to leave the unit powered up for a couple of days, it seemed like the longer it was on, the lower I could set the frequency and not have to use the un-calibrated vernier setting (capacitors reforming??) and see where it's at.
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- I have not compared it to my HP 333A yet, but I have hooked up a couple of other sig gens that I have just to see its operation, results seemed reasonable
- Other than the output monitor being dead, it seems like it just might need an alignment/calibration
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I have some equipment (HP pulse generator, scopes, freq. counters, etc.), but nothing calibrated by a lab, just a semi-serious hobby for me - testing/repairing my own stuff.
I have not looked at the supply rails with a scope yet, I have looked at the output - looks like a nice sine wave.
I will review the schematic for the output monitor, but I am not hopeful if it turns out to be an active device (finding replacement transistors are pretty much unobtanium nowadays, it seems).
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Suggestions , opinions on where to go next?
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sorry for the TL;DR
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Thanks,
Jim
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I gotta say, I just love seeing the gold PCB traces on this era's equipment - no tin-wiskers here! I smile every time I open up this type of equipment.
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Re: HP 141T Power Supply Help Needed
¿ªÔÆÌåÓýFrank, ? I appreciate your calculations.? Bill¡¯s problem is more fundamental than exact calculations would suggest.? It seems that since the voltage at C6 (the bulk capacitor) is so low (<1V) that there must be a wiring problem, or the diodes are bad, or the power transformer has a bad winding (which is very unlikely).? Bill says that he checked the diodes so the only thing left is a broken wire somewhere.? That is the way I see it. ? Mike ? From: [email protected] <[email protected]> On Behalf Of Frank Mashockie
Sent: Saturday, September 7, 2024 12:29 PM To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP 141T Power Supply Help Needed ? Mike, ? Wouldn't it be ~27VAC across the winding (11 and 13)? Or ~13.5VAC at both 11 and 12 and 13 and 12?? For a center tapped full wave rectifier Vout = Vp (sec)/2 - diode drop.? Since the center tap is -12.6V and you have 6.0VDC at the output, if we make -12.6V ground, you have Vout = 18.6VDC.? (18.6 + ~0.7)x2 = 38.6Vp.? 38.6 x square root 2 = 27VAC in rms across the winding from pins 11 to 13. Or am I missing something? ? -Frank? |
Re: Leaking alkaline cells
The whole discussion of battery reliability reminds me of another issue a couple of decades ago.?I was on a project that had to store many images in an image library. CDROMs were one option were they reliable? I found a ?NIST? report on the archival properties of writeable CDROMs. They investigated many different types from many different manufacturers; some were useful for archiving within acceptable limitations, some weren't. From memory, the main parameters were the chemistry of the writeable layer, and the top-surface protective layer. The writeable layers came in a few colours. Some colours were always unusable, some were usable depending on the specific chemistry involved - but you couldn't tell the difference by simple observation. On top of that, each manufacturers tended to sell a variety of chemistries without specifying which you would get.?In essence the brands appeared to be little more than names applied to whatever they could source this month.? Thus the only way to tell whether a batch of CDROMs was suitable for archival purposes was to test them for that. Not helpful. |
looking for a scan of the HP8901A pull out reference card
I am looking for a pull out reference card for the HP8901A modulation analyser.
Mine used to be rackmounted and lost its card in the mists of time. Now that I have repaired its PSU it is time to stick it into my ham shack.
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A ?hi-res scan would be great, who can help me please? Sofar drew blanks on Google e.a.
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Vy73 Wilko |
Re: Leaking alkaline cells
Morris,
I've just checked the pack I bought them in and it says (proudly and in several places) "Made in Germany" so it would seem the ones available in the antipodes are made to an inferior standard under licence - presumably - somewhere else on the planet. I can't ever recall having had an issue with Varta batteries and I use them preferentially in everything I value. Duracell really needs to take a long, hard look at itself. |
Re: Leaking alkaline cells
Forgive me if I missed something but I have not been following this thread very closely.
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I'm not saying they were wrong, but weren't environmentalists behind the EPA forcing removal of mercury from alkaline cells?? The mercury was present to reduce the tendency to evolve hydrogen gas which swelled the cells or caused them to leak.? 1996 time frame for enactment of the rule/law.? Link:
My memory is that was the beginning of the end for alkaline reliability.? It would appear that as with? Tetraethyllead in fuels, the industries never came up with a a good replacement for the environmental toxin they had to remove.? Some countries may still make cells with traces of mercury, the US pretty much banned it except for button cells.? Considering how many of those have leaked since the ban started I assumed they removed it from them as well.? Button cells almost never leaked, now leaks are common.? I don't know which or if all other countries have banned mercury in batteries.? China only banned it in 2021 (a 2017 law).
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I have a large number of dead alkaline cells in a jar many of them have leaked since they were removed but quite a few leaked before being fully depleted.? Both Duracell and Energizer batteries are leaking, more the longer they have been depleted.? I have seen leakage in a new cell from a large pack as well.? The variabil;ity is probably due to manufacturing process variations in the seals.? I had one small lot of batteries that all leaked shortly after depletion.? Fortunately I used most of those on my wireless mice and keyboards so they were removed before they leaked but they leaked before I put them in the recycle jar.? It took a couple of years to use them up, but the age didn't seem to matter, just once they were below 1 volt, leakage was imminent.?
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Clay |
Re: Leaking alkaline cells
I think the only Varta batteries I've used are for my watch and I think I got them from Barry - N4BUQ?
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Re: HP 5086-7906 YTO
¿ªÔÆÌåÓýHi Adri ? Here are the measurements connected to the first 2 converters as a reference. ? For the second converter I get a voltage of -1.678V instead of -3.5V as written in the service manual, I would say that we have similar voltages for this particular point. It seems far from the nominal point, but there may be an error in the manual. ? You are close to the goal, and this module may be repairable if there is no micro circuit, I have never opened a second converter in this series, but it is a possibility. ? When you open your second converter, send me pictures, I'm curious. ? Yves De?: [email protected] <[email protected]> De la part de alfa beta ? dear Yves, I didn't realize that you had made the measurements expressly to help me! I owe you then a double (even triple) thanks! Especially considering the fact that the front end of this instrument is really very dense, complicated and delicate! After my last email, in addition to doing the (essentially mechanical) intervention on the SYTF, I continued to check the input signal through the various sections by alternately injecting 300MHz @-20dBm and 5GHz @0 dBm The signals were found to be in specification up to the A3A9 bandpass (where the two paths join to form the intermediate frequency of 321.4MHz). At this point I could see the 5GHz signal (converted), present at that point at -47dBm (the specification says -43/-56dBm).
? This last value is rather far from the nominal and would have worried me BUT band 1 is exactly the one that works Conclusion: it would seem that the culprit is the second converter and in particular (probably) the internal switch that has the sole task of letting the signal? (which is already at 321.4MHz and does not need to be converted)?pass from its input to the output
? Actually,?this connector on the real component, does not have a name Now,?on the block diagram the connector that conveys the 600MHz signal has the name J4 (in my analyzer, the J4 connector was disconnected) ? This confusion of names and roles made me doubt that years ago, when I had disassembled this section I had not reassembled it correctly thanks again and best regards Adri ? ? ?
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Re: Leaking alkaline cells
On Sat, Sep 7, 2024 at 07:55 PM, Jinxie wrote:
Thanks Jinxie, ?
I don't have any Vartas here in my recycle box but next time I'm at a store I'll check them out. I suspect they are made in China like just about everything else these days.
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Morris |
Re: Leaking alkaline cells
Sure, take some flour and throw a cloud of it and light a match and it will explode.? But it won't do that normally.
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On 9/7/2024 5:58 PM, Chuck Harris via groups.io wrote:
A gander at youtube will find all sorts of daring do'ers that take |
Re: Leaking alkaline cells
A gander at youtube will find all sorts of daring do'ers that take
apart the AA cell lithium replacements for alkaline cells, unwrap the lithium foil, and make them sizzle spit and spark, and catch fire. Might be impossible in the can, but I see lots of impossible failures regularly. -Chuck Harris On Sat, 7 Sep 2024 01:03:59 -0400 "Peter Gottlieb" <hpnpilot@...> wrote: In practice a small leak won¡¯t cause anything spectacular. The |
Re: HP 141T Power Supply Help Needed
Mike,
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Wouldn't it be ~27VAC across the winding (11 and 13)? Or ~13.5VAC at both 11 and 12 and 13 and 12?? For a center tapped full wave rectifier Vout = Vp (sec)/2 - diode drop.? Since the center tap is -12.6V and you have 6.0VDC at the output, if we make -12.6V ground, you have Vout = 18.6VDC.? (18.6 + ~0.7)x2 = 38.6Vp.? 38.6 x square root 2 = 27VAC in rms across the winding from pins 11 to 13. Or am I missing something?
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-Frank? |
Re: HP 141T Power Supply Help Needed
¿ªÔÆÌåÓýBill, ? 1.5V across R40 which is the bleeder resistor for the -12.6 bulk supply is definitely a problem.? There are only a few things that can cause that.? The next thing to do is check the voltage at the cathodes of CR1 and CR2.? If you don¡¯t have 24VDC there; check the AC voltage at the anodes of CR1 and CR2.? If the diodes check good then the wiring is open somewhere.? There only a few things left.? Lets hope that you have 24VAC at the terminals 11 to 12 and 12 to 13 on the power transformer.? If you don¡¯t have voltage at the power transformer you have a bad power transformer and those are almost impossible to find.? ? Best if luck, Mike ? From: [email protected] <[email protected]> On Behalf Of Bill Berzinskas
Sent: Saturday, September 7, 2024 11:09 AM To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP 141T Power Supply Help Needed ? Mike? Agree we've been through it all by now.? ?I did find a bad trace to the base of C11, I jumpered R45 straight over to it.?? Across r40 I get 1.5v.?? At c6 I get -0.5v.?? 24v at diodes seems OK.?? Cr1 and 2 test OK.? Frank, I do have it isolated. And I have been replacing passives as I find?them.?? Maybe part of the issue.?? I'm thinking maybe diodes aren't appropriate..? ?? ? On Sat, Sep 7, 2024, 12:45?AM Frank Mashockie via <fmashockie=[email protected]> wrote:
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Re: HP 141T Power Supply Help Needed
Mike? Agree we've been through it all by now.? ?I did find a bad trace to the base of C11, I jumpered R45 straight over to it.?? Across r40 I get 1.5v.?? At c6 I get -0.5v.?? 24v at diodes seems OK.?? Cr1 and 2 test OK.? Frank, I do have it isolated. And I have been replacing passives as I find?them.?? Maybe part of the issue.?? I'm thinking maybe diodes aren't appropriate..? ?? On Sat, Sep 7, 2024, 12:45?AM Frank Mashockie via <fmashockie=[email protected]> wrote:
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Re: Leaking alkaline cells
"Dead batteries given away free of charge."
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On 9/7/2024 7:14 AM, Michael Kellett via groups.io wrote:
For a long time now I've used nothing but the industrial versions of Duracells. They used to be marketed as Industrial by Duracell and now as Procell. |