Much like my fix for the last 5342A I picked up, just reseated all the boards (more of a case of the contacts needed a clean), I’m glad you found that loose board before digging in too deeply! I wish I could find auction scores like that in my country!
Thanks. BTW, did you do a key cleaning with your 5342A? I have one that needs cleaning but I'm not sure if it is worth videoing it. If you've already shown that ten I'll probably skip it.
Looking for some insight regarding the cooling fan on a HP 438. A recent acquisition of two HP 438s from the FAA, current cal pass, but one cooling fan squeals like it has a bad bearing and the other fails to rotate when powered. Four leads between the fan and its power or control module and from there a lead to 10.4V and the other lead to Grnd. HP and the mfg Buhler part number are the same, p/n 00438-60047. I understand the need to isolate the fan from anything else on this 10.4V circuit, but what is with this fan and the control module? Can this fan, a search for which found nothing, be replaced with a 12V fan? Is the fan trying to control the temp within a narrow range, or just keep the components cool?
That's a great question - Unfortunately I've never looked into it - I believe there are just the two inputs to the motor control module and the fan has 3 coils but I'm really not sure what the control is doing - I think it's just a DC fan but I've never looked into it - My recommendation is to jump over to the HPAK group on groups.io and ask there about replacement fans as I'm sure someone will have done that.
This reminds me of one of those tektronix modules for the TM500 series (TestMate I believe its called). I had a rare but malfunctioning power extension module (hard to describe because its not a standard piece of kit). It basically supplies all the power rails but gives a green or red light if all is working or not. It was giving a green light for a good while then red then no lights which was very odd. I thought the IC made in the 70s finally gave. Further, the fuses looked kinda burned but were still making a connection. Before I took the IC out of its socket I decided to do a continuity check to map for a schematic of the module. Turns out I just so happened to notice that the edge connector's solder cracked and split from the PCB due to years of just plugging in and out. It was making intermittent contact from trace pads to the connector. I also guess heat expansion had a play in it too. Just reflowed everything and back in business. As for the fuses, to this day I'm not sure. Guess someone ran short and decided to reuse old nearly burnt fuses because everything works better than ever even with the burnt fuses. I did replace those fuses anyways after testing. By the way I noticed that your 3rd 438A has its cover upside down. ;)
I wondering about that case, I didn't think they went back together that way. Anyway, always nice to have a simple fix like his one. As for your connector, I had the same problem for the GPIB connector on a 11713A. I think it happens way more than people think.
@@tgsoapbox Yes, just like the video you did on the 437B. How to choose the sensor (if there is an option to choose) and calibrate it for the measuring. Also since it has two sensor ports whether there is any additional things to be concerned with. And if there is any difference or advancement in the 438 compared to other members of this series 435, 436 abd 437.
Much like my fix for the last 5342A I picked up, just reseated all the boards (more of a case of the contacts needed a clean), I’m glad you found that loose board before digging in too deeply!
I wish I could find auction scores like that in my country!
Thanks. BTW, did you do a key cleaning with your 5342A? I have one that needs cleaning but I'm not sure if it is worth videoing it. If you've already shown that ten I'll probably skip it.
tgsoapbox - no I just sprayed some Isopropyl Alcohol and operated them, they were working ok, but clicky, needed a touch of WD40.
With all the things that can and do go wrong, it sure is nice to get lucky once in a while. Good job and thanks for sharing.
Looking for some insight regarding the cooling fan on a HP 438. A recent acquisition of two HP 438s from the FAA, current cal pass, but one cooling fan squeals like it has a bad bearing and the other fails to rotate when powered. Four leads between the fan and its power or control module and from there a lead to 10.4V and the other lead to Grnd. HP and the mfg Buhler part number are the same, p/n 00438-60047. I understand the need to isolate the fan from anything else on this 10.4V circuit, but what is with this fan and the control module? Can this fan, a search for which found nothing, be replaced with a 12V fan? Is the fan trying to control the temp within a narrow range, or just keep the components cool?
That's a great question - Unfortunately I've never looked into it - I believe there are just the two inputs to the motor control module and the fan has 3 coils but I'm really not sure what the control is doing - I think it's just a DC fan but I've never looked into it - My recommendation is to jump over to the HPAK group on groups.io and ask there about replacement fans as I'm sure someone will have done that.
This reminds me of one of those tektronix modules for the TM500 series (TestMate I believe its called). I had a rare but malfunctioning power extension module (hard to describe because its not a standard piece of kit). It basically supplies all the power rails but gives a green or red light if all is working or not. It was giving a green light for a good while then red then no lights which was very odd. I thought the IC made in the 70s finally gave. Further, the fuses looked kinda burned but were still making a connection. Before I took the IC out of its socket I decided to do a continuity check to map for a schematic of the module. Turns out I just so happened to notice that the edge connector's solder cracked and split from the PCB due to years of just plugging in and out. It was making intermittent contact from trace pads to the connector. I also guess heat expansion had a play in it too. Just reflowed everything and back in business. As for the fuses, to this day I'm not sure. Guess someone ran short and decided to reuse old nearly burnt fuses because everything works better than ever even with the burnt fuses. I did replace those fuses anyways after testing. By the way I noticed that your 3rd 438A has its cover upside down. ;)
I wondering about that case, I didn't think they went back together that way. Anyway, always nice to have a simple fix like his one. As for your connector, I had the same problem for the GPIB connector on a 11713A. I think it happens way more than people think.
Hi, @tgsoapbox Can you do a video on calibrating the RF power sensors with this HP438A power meter, pls? using 8484A or 8481A
Do you mean how to connect the sensor and calibrate it before a reading?
@@tgsoapbox Yes, just like the video you did on the 437B. How to choose the sensor (if there is an option to choose) and calibrate it for the measuring. Also since it has two sensor ports whether there is any additional things to be concerned with. And if there is any difference or advancement in the 438 compared to other members of this series 435, 436 abd 437.
@@SuperhoouGot it - Give me a bit and I'll sort it out - I think I still have a 438A here.
@@tgsoapbox Thank you so much!