HP339 Repair Thread

Zero Cool · 23rd August 2008, 03:32 AM

I got my HP339 the other day. it powers up but has some problems. 1st is that there is some 60 cycle hum in the output causing problems. I replaced the power supply capacitors and the local 47uf caps on the oscillator board but the issue inst any better.

wiggling things around i got the noise to go away. I think the problem is that Internally they used some switchcraft branded RCA cables to run the signla from place to place and the crowns of all the RCA plugs have some heavy white oxidation on them. scraping the white crusty stuff off reveals a dark colored metal below. I'm not sure how well i will be able to get these clean. Replacing them with exact length cables is next to impossible as each one is custom made. I don't know how comfortable i would be making new cables and keeping things within spec.

Any suggestions on how to clean these rca plugs?

Zc

Zero Cool · 24th August 2008, 03:03 PM

I found a tiny ceramic tipped polishing bit for my dremel tool and got inside those rca connectors and cleaned them all out so that make a good ground contact. I also found cracked solder joints on the main transformer harness plug/pc board connection and fixed those up. Now the unit seems to be running a lot more stable!

I also discovered that the Oscillator section is ground isolated and that was part of my noise issue. I was grounding my scope lead to the chassis ground lug and the Osc section is completely isolated from the chassis. Once I connected the scope lead to the Osc output ground, the 60 cycle hum went away! Imagine that!

The next issue i need to tackle is power on surge. when you power the unit on the meter pegs for several seconds then settles down. I cant imagine it is meant to be this way. So i need to get in there and figure out whats causing that. bad capacitor someplace maybe. But thus far all caps have tested good. I have replaced them anyway but none have been open or shorted. You just cant go wrong buying old used HP test gear. heck if nothing else those gold plated boards are pretty to look at hahahahha

I have been able to loop the osc to the dist anyl. input and get the meter to show about mid scale with the knob down to -80db. need to read through the manual and figure out how to read the meter scale and what not and i have been able to seen the residuals on my scope screen and learned why its not a good idea to have florescent lights in a shop with electronic ballast's!! tons of HF noise that went away when i kicked in the Lowpass filters!

I was pleased with the tests. it appears to be working thus far and shows promise of being a usable unit with a bit more work!

tschrama · 24th August 2008, 03:15 PM

I have a HP339A for 6 months now (or about)... and allthough it works nicely, I would be very interested in some pics and your repair progress.. just I case I might need to repair it some day..

btw do you have the service manual? I'm not sure, but if I have it I could send it to you..

Zero Cool · 24th August 2008, 06:13 PM

Hello,

I will take some pics next time i am at my shop! I do have the service manual but the parts list's sections are blurry. the first half of the manual is clear but the 2nd half gets unreadable on some sections. the schematics are clear so it is usable at least. But the schematic sections are broken up across several pages for each section making it hard to follow. I have been using photoshop to splice the pages together to make it easier.

Is your manual better??

BTW. when you power your 339 on, does the needle slam to the right and stay there for a few seconds then settle down?? I don't think that is normal and i need to figure out why it does that.

q2audio · 18th September 2008, 10:35 PM

I just got one of these - I used to use them at a previous job and really liked them. This one also pegs the meter at turn on, I seem to recall this as being normal. I also have a HP 403B dB meter that does the same thing. I think it takes a few seconds for the DC part of the circuit to settle down.

Very interesting about the white crud around the RCA connectors. I may try wiggling these to see if that is related to my problem: intermittent/high readings in the distortion mode. In the manual available from the HP (Agilent) site, they mention mods to get rid of a 300Khz oscillation but not in detail. It involves putting a ferrite (FE) bead around the leads of a couple of IC's on one of the PCB's. I think the loop back test should give you nearly a 0.001% reading.

I used flux remover on cotton swabs and cleaned the rotary switch moving contacts. They were filthy with brown crap that I think used to be grease. This has not improved my stability problems but I was amazed at how dirty the swabs were!

If you were to make new RCA cables, I don't think I would worry too much about them, use a good quality wire and decent ends (I like the Neutrik RCA's for about $1 ea - for test purposes). What is in there looks pretty low end (molded ends, etc.).

These things are beautiful on the inside...

Tim

jackinnj · 19th September 2008, 02:27 PM

Quote:

Originally posted by tschrama
I have a HP339A for 6 months now (or about)... and allthough it works nicely, I would be very interested in some pics and your repair progress.. just I case I might need to repair it some day..

btw do you have the service manual? I'm not sure, but if I have it I could send it to you..

The manual should be available on Agilent's website.

Apex Jr · 19th September 2008, 02:38 PM

Just curious...
What are these going for on the surplus market
or what did you pay for yours.

Steve @ Apex Jr.

Zero Cool · 19th September 2008, 03:12 PM

Quote:

Originally posted by Apex Jr
Just curious...
What are these going for on the surplus market
or what did you pay for yours.

Steve @ Apex Jr.

Well according to eBay, used and working is about $400-600 I got mine in unknown condition for $125 It had some bad solder joints and needed the Internal RCA connectors cleaned up but it seems to work. I'm not sure if it has other issues or not thus far. when powering up it slams the needle full peg which concerns me. I can't imagine thats normal? so i need to look into that.

but it generates a clean signal. and i have been able to observe distortion residuals on my scope with it thus far so thats at least a good sign that there is hope that this will be usable.

I wouldn't mind finding a parts unit if someone has one. I need one button and maybe one switch for mine. Have you got one thats about to be for sale??

Zc

Apex Jr · 19th September 2008, 03:49 PM

Yes, I have one in stock, I paid a bit more.
I haven't plugged it in in a while but It came
from a company using it and out of business.

I do go to an electronic swap meet once a month a
will keep my eyes open for a parts unit

Steve @ Apex Jr.

23rd August 2008, 03:32 AM	#1
Zero Cool Audio Junkie diyAudio Member Join Date: Sep 2004 Location: MN	HP339 Repair Thread I got my HP339 the other day. it powers up but has some problems. 1st is that there is some 60 cycle hum in the output causing problems. I replaced the power supply capacitors and the local 47uf caps on the oscillator board but the issue inst any better. wiggling things around i got the noise to go away. I think the problem is that Internally they used some switchcraft branded RCA cables to run the signla from place to place and the crowns of all the RCA plugs have some heavy white oxidation on them. scraping the white crusty stuff off reveals a dark colored metal below. I'm not sure how well i will be able to get these clean. Replacing them with exact length cables is next to impossible as each one is custom made. I don't know how comfortable i would be making new cables and keeping things within spec. Any suggestions on how to clean these rca plugs? Zc

18th September 2008, 10:35 PM	#5
q2audio diyAudio Member Join Date: Sep 2007	HP339A I just got one of these - I used to use them at a previous job and really liked them. This one also pegs the meter at turn on, I seem to recall this as being normal. I also have a HP 403B dB meter that does the same thing. I think it takes a few seconds for the DC part of the circuit to settle down. Very interesting about the white crud around the RCA connectors. I may try wiggling these to see if that is related to my problem: intermittent/high readings in the distortion mode. In the manual available from the HP (Agilent) site, they mention mods to get rid of a 300Khz oscillation but not in detail. It involves putting a ferrite (FE) bead around the leads of a couple of IC's on one of the PCB's. I think the loop back test should give you nearly a 0.001% reading. I used flux remover on cotton swabs and cleaned the rotary switch moving contacts. They were filthy with brown crap that I think used to be grease. This has not improved my stability problems but I was amazed at how dirty the swabs were! If you were to make new RCA cables, I don't think I would worry too much about them, use a good quality wire and decent ends (I like the Neutrik RCA's for about $1 ea - for test purposes). What is in there looks pretty low end (molded ends, etc.). These things are beautiful on the inside... Tim

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24th August 2008, 03:03 PM	#2
Zero Cool Audio Junkie diyAudio Member Join Date: Sep 2004 Location: MN	I found a tiny ceramic tipped polishing bit for my dremel tool and got inside those rca connectors and cleaned them all out so that make a good ground contact. I also found cracked solder joints on the main transformer harness plug/pc board connection and fixed those up. Now the unit seems to be running a lot more stable! I also discovered that the Oscillator section is ground isolated and that was part of my noise issue. I was grounding my scope lead to the chassis ground lug and the Osc section is completely isolated from the chassis. Once I connected the scope lead to the Osc output ground, the 60 cycle hum went away! Imagine that! The next issue i need to tackle is power on surge. when you power the unit on the meter pegs for several seconds then settles down. I cant imagine it is meant to be this way. So i need to get in there and figure out whats causing that. bad capacitor someplace maybe. But thus far all caps have tested good. I have replaced them anyway but none have been open or shorted. You just cant go wrong buying old used HP test gear. heck if nothing else those gold plated boards are pretty to look at hahahahha I have been able to loop the osc to the dist anyl. input and get the meter to show about mid scale with the knob down to -80db. need to read through the manual and figure out how to read the meter scale and what not and i have been able to seen the residuals on my scope screen and learned why its not a good idea to have florescent lights in a shop with electronic ballast's!! tons of HF noise that went away when i kicked in the Lowpass filters! I was pleased with the tests. it appears to be working thus far and shows promise of being a usable unit with a bit more work!

24th August 2008, 03:15 PM	#3
tschrama diyAudio Member Join Date: Jul 2001 Location: The Netherlands	I have a HP339A for 6 months now (or about)... and allthough it works nicely, I would be very interested in some pics and your repair progress.. just I case I might need to repair it some day.. btw do you have the service manual? I'm not sure, but if I have it I could send it to you..

24th August 2008, 06:13 PM	#4
Zero Cool Audio Junkie diyAudio Member Join Date: Sep 2004 Location: MN	Hello, I will take some pics next time i am at my shop! I do have the service manual but the parts list's sections are blurry. the first half of the manual is clear but the 2nd half gets unreadable on some sections. the schematics are clear so it is usable at least. But the schematic sections are broken up across several pages for each section making it hard to follow. I have been using photoshop to splice the pages together to make it easier. Is your manual better?? BTW. when you power your 339 on, does the needle slam to the right and stay there for a few seconds then settle down?? I don't think that is normal and i need to figure out why it does that.

19th September 2008, 02:38 PM	#7
Apex Jr diyAudio Member Join Date: Jun 2002 Location: Torrance, Calif	Just curious... What are these going for on the surplus market or what did you pay for yours. Steve @ Apex Jr.

19th September 2008, 03:49 PM	#9
Apex Jr diyAudio Member Join Date: Jun 2002 Location: Torrance, Calif	Yes, I have one in stock, I paid a bit more. I haven't plugged it in in a while but It came from a company using it and out of business. I do go to an electronic swap meet once a month a will keep my eyes open for a parts unit Steve @ Apex Jr.

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