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HP 130A restoration
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Hi, I started to repair a HP 130A scope in Milano, Italy, and I am presently trying to extract the CRT from the case.
The manual says
I am not succeeding in "loosing the CRT base from the socket" and I am worried to brake it.
Does anybody of you have any experience in doing it?
Another issue I am having is that I see small inconsistencies between the manual (serial 125) I got from the HP repository and reality ( serial 2482) . For example V20 is a 6BQ7A on the tube replacement chart but a 12AU7 in reality and as printed on the scope frame. Any newer manual around?
I am interested practically in any non trivial info concerning my project, thanks to all, Pepi
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CRT problemi solved, thanks Bob, still looking for a schematic for my model number
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Don Bitters
On Thu, Mar 21, 2024 at 06:12 AM, Don Bitters wrote:
HP-130A-Manual
As said earlier the archive serial N is 125 while mine is 2482 and it looks like there are serious differences between the two models.
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I just received from Ebay an original manual (mod 25 to 724) with schematics which are completely readable, in the fine print parts too, which is not the case for the one I found on the web. If anybody needs them i'll be more than happy to make copies, in fact I think I'll post a new high res copy on this group. I still have the problem to find out which modifications have occurred in my model which is N 2482, if anybody knows I would be happy to find out, thanks, Bepi
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I am stuck again at the power supply level, somebody (sorry I forgot who, it must have been a private message) already told me to unplug the HV valves and start to check the lower DC voltages, a very useful suggestion which I followed.
All the AC voltages are there but the rest doesn't come up right.
the 88V is 31V and the -150 is next to 0
The v31 rectifier works and is anode V goes up to 300
then the fuse blows
In summary what I don't understand from the schematic is if I can unplug components (valves) to check each section separately, or additively until I get to the faulty components because they seem all interconnected. Could anybody help please?
The relevant schematic is
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I'm struggling to read some of the numbers on the circuit diagram, for the power supply section.
It looks like two of the power supply valve filaments are dependant on the +88V DC supply, the rest of the power supply sections are dependant on the -150V supply.
I would start measuring voltages on V32, V33 and the voltage reference tube V34 (does this glow?), the fuse blowing will probably prevent you from doing this. Voltages expected are shown on page 38.
Did you manage to sort out a lamp limiter (aka dim bulb tester) to use instead of the variac? you would need to experiment to find a high enough wattage lamp to allow the valve filaments to work and the fuse to stay intact for fault finding.
In the other thread I wasn't aware you are located in Italy, is the transformer set for 110V or 230V operation.?Mine was imported from the USA to the UK and I've changed the connections for 230V operation.
David
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Based on my experience with similar HP scopes (132, 140, 175), I’d say the -150 supply is the reference for all of the others. Pull all the power supply tubes and see if you can bring up the line voltage without blowing any fuses. Failure at this point would be a transformer short circuit or some component connected across the AC line or one of the secondary windings. Then install the tubes in the -150V supply and get it working. I?
Once you have -150V DC, you can gradually return tubes to the other sections, one section at a time, and get them working.?
I'm struggling to read some of the numbers on the circuit diagram, for the power supply section.
It looks like two of the power supply valve filaments are dependant on the +88V DC supply, the rest of the power supply sections are dependant on the -150V supply.
I would start measuring voltages on V32, V33 and the voltage reference tube V34 (does this glow?), the fuse blowing will probably prevent you from doing this. Voltages expected are shown on page 38.
Did you manage to sort out a lamp limiter (aka dim bulb tester) to use instead of the variac? you would need to experiment to find a high enough wattage lamp to allow the valve filaments to work and the fuse to stay intact for fault finding.
In the other thread I wasn't aware you are located in Italy, is the transformer set for 110V or 230V operation.?Mine was imported from the USA to the UK and I've changed the connections for 230V operation.
David
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Apparently V30 & V33 have their heaters fed from the +88V rail, in the series string of 8 valves, having only +31V is going to prevent the control valve/tubes from working in the -150V & +88V, seems these rails are dependant on each other.
David
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OK, I see that now—schematic is hard to read. Agree, looks like the two sections depend upon each other.?
Apparently V30 & V33 have their heaters fed from the +88V rail, in the series string of 8 valves, having only +31V is going to prevent the control valve/tubes from working in the -150V & +88V, seems these rails are dependant on each other.
David
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If that heater string is open, the +80 and -150 volt supplies should run wide open, because the control tubes would be nonconducting.
Hugh
OK, I see that now—schematic is hard to read. Agree, looks like the two sections depend upon each other.?
Apparently V30 & V33 have their heaters fed from the +88V rail, in the series string of 8 valves, having only +31V is going to prevent the control valve/tubes from working in the -150V & +88V, seems these rails are dependant on each other.
David
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Very interesting i didn't realize some heaters are run in series. I checked the cold resistance of the 88V heaters and is 126 ohm which divided by 14 heaters makes 9 ohm, about right for a single 6.3 V cold heater.
Factory I don't understand the bulb idea completely. Presently the scope absorbs slightly less than 100W, and the fuses would allow for roughly 200W, it's a 2A fuse. If I put a 100W bulb in series the heaters will not heat up enough but with a 200W bulb a short would blow up the fuse. Should I put a 300 W bulb in series and a larger fuse, like 2 or 4 A?
The reason I am hesitant is that my variac is 110V, following a 220 to 110 transformer and at the moment the power cord current runaway, with all the tubes in, is slow enough that I can turn the variac off before blowing the fuse. Most of the time.
Finding an array of large 110V bulbs in Italy now is out of the question.
Anyway I am making progress, unplugged the N 9 & 10 connectors from the 88 V PS board and got around -160 V, not quite -150 but with no load. Is it already time to trim this supply to its correct voltage?
Tomorrow I'll check the 88 V supply.
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Sorry a correction, by disconnecting the J9P interpanel connector I have disconnected the V33 heater so I could not have had the right voltage out anyway from the -150 supply, regardless I was getting around -165 on C140B. The dV across V34, 80+V, is about right.
Riconnecting J9P only and not J10P the 88V supply should not have worked regularly also since there the 300 V supply contribution is missing? , I am getting 31V instead of 88. Around 200V on the V28 and V29 plates. I tried to regulate the 150V supply and I could do this verya ccurately.
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I’ll have to look at the schematic again, as I didn’t notice the dependence (also) of 88V on the 300V supply. HP simplified their ‘scope power supplies subsequently, making one supply the standard for regulating all the others.?
Sorry a correction, by disconnecting the J9P interpanel connector I have disconnected the V33 heater so I could not have had the right voltage out anyway from the -150 supply, regardless I was getting around -165 on C140B. The dV across V34, 80+V, is about right.
Riconnecting J9P only and not J10P the 88V supply should not have worked regularly also since there the 300 V supply contribution is missing? , I am getting 31V instead of 88. Around 200V on the V28 and V29 plates. I tried to regulate the 150V supply and I could do this verya ccurately.
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One more generic question: up to now I have never seen any evidence that the CRT is working, if I get to the point of having the whole circutry working again and I discover that the CRT is not recoverable will I be able to find a replacement? I already checked the heater and that one seems to have the right resistance, the look of the gettered surface seems to have the right look too. Thank you for your comments.
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If the CRT has an intact heater & shiny silver getter, it is probably fine. Lack of EHT is more likely to be a problem, especially if there are leaky paper based capacitors in the EHT circuit, or a bad step up transformer.
Also there are several 5AQP type CRTs on ebay, two which look to have been pulled from old oscilloscopes and one very expensive NOS.
David
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I found the main power supply issue, a blown capacitor in the HV section, one side to ground. Unplugging the tubes was not enough to exclude the HV section. From the schematic?  I notice that the blown capacitor C112 has a sister one C111 , same value, according to the component list 0.1 uF  if I measure the good one i get a 3 times bigger value? (this Chinese res/cap/ind/diode/transistor 3$ is amazingly useful)  ?and the resistor in between measures 45 ohm instead of 100. Can anybody read the capacitor color codes? Reality is different from the schematic , the manual is for mod 25 to 724, mine is N 2482I am tempted to go with the schematic and replace the original capacitors with polyester ones I already purchased, .1uF 650V, am I doing the right thing?
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Replacing both C111 and C112 with your purchased parts won’t be a?problem.? N6WFO?
I found the main power supply issue, a blown capacitor in the HV section, one side to ground. Unplugging the tubes was not enough to exclude the HV section.
From the schematic?
I notice that the blown capacitor C112 has a sister one C111 , same value, according to the component list 0.1 uF
if I measure the good one i get a 3 times bigger value? (this Chinese res/cap/ind/diode/transistor 3$ is amazingly useful)
?and the resistor in between measures 45 ohm instead of 100. Can anybody read the capacitor color codes?
Reality is different from the schematic , the manual is for mod 25 to 724, mine is N 2482
I am tempted to go with the schematic and replace the original capacitors with polyester ones I already purchased, .1uF 650V, am I doing the right thing?
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If I'm not mistaken, brown,black,yellow,white(silver?),yellow -> 100,000pF, not sure of the tolerance (white, silver?), 400V.
Barry - N4BUQ
From: "Bepi" <pepicima@...>
To: "HP-Agilent-Keysight-equipment" <[email protected]>
Sent: Wednesday, May 8, 2024 10:27:44 AM
Subject: Re: [HP-Agilent-Keysight-equipment] HP 130A restoration
I found the main power supply issue, a blown capacitor in the HV section, one side to ground. Unplugging the tubes was not enough to exclude the HV section.
From the schematic?
I notice that the blown capacitor C112 has a sister one C111 , same value, according to the component list 0.1 uF
if I measure the good one i get a 3 times bigger value? (this Chinese res/cap/ind/diode/transistor 3$ is amazingly useful)
?and the resistor in between measures 45 ohm instead of 100. Can anybody read the capacitor color codes?
Reality is different from the schematic , the manual is for mod 25 to 724, mine is N 2482
I am tempted to go with the schematic and replace the original capacitors with polyester ones I already purchased, .1uF 650V, am I doing the right thing?
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Those are considered "bumblebee's".? Generally, speaking, they were bad if they made a noise when you threw them in the trash.?
If I'm not mistaken, brown,black,yellow,white(silver?),yellow -> 100,000pF, not sure of the tolerance (white, silver?), 400V.
Barry - N4BUQ
From: "Bepi" <pepicima@...>
To: "HP-Agilent-Keysight-equipment" <[email protected]>
Sent: Wednesday, May 8, 2024 10:27:44 AM
Subject: Re: [HP-Agilent-Keysight-equipment] HP 130A restoration
I found the main power supply issue, a blown capacitor in the HV section, one side to ground. Unplugging the tubes was not enough to exclude the HV section.
From the schematic?
I notice that the blown capacitor C112 has a sister one C111 , same value, according to the component list 0.1 uF
if I measure the good one i get a 3 times bigger value? (this Chinese res/cap/ind/diode/transistor 3$ is amazingly useful)
?and the resistor in between measures 45 ohm instead of 100. Can anybody read the capacitor color codes?
Reality is different from the schematic , the manual is for mod 25 to 724, mine is N 2482
I am tempted to go with the schematic and replace the original capacitors with polyester ones I already purchased, .1uF 650V, am I doing the right thing?
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factory
Jeremy Nichols