I don't contribute for money. BUT if someone is going to do all this upgrade work etc and then sell it.... that's OK. IMO. If it isn't an expensive selling price. A little more than cost - for time - seems in the right spirit. Otherwise... I wants my cut.
THx-RNMarsh
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Hi,
Going by memory only... If it isn't corroded contacts --- there is a fuse and a relay contacts in series with the osc output. One could be open.
THx-RNMarsh
I guess I missed the earlier posts by Sync from months back about the mad 339A mod pirate. Yes, That was my 339A that sold for $425 on Ebay. Not that it should be that hard to figure out, the sellers city is in the Ebay listing and my city is shown in my signature on DIYAUDIO here and the names are similar.
Just an FYI,
I paid about $200 shipped for that 339A in “unknown” condition. I probably paid another $40 – 50 for the parts and pieces I put into the unit counting shipping and tax into the mix. A couple of knobs were broken and I had to source some replacements. I also had at a minimum 12 hours or more involved with the unit between recapping the power supply, hand cleaning all of the switch wafers and then performing the diyaudio mods. Remember that after selling anything on Ebay they keep 10% and Paypal another 3% of the auction total.
Add that up and factor in the hours of labor! If anyone really thinks that’s a profitable enterprise I’ve got to wonder what you do for a living. If I had sold it for $900 then I might see where you could complain.
Anyway, there’s currently two HP 339A’s in the Ebay completed auctions listings right now with NO mods and NO maintenance or testing whatsoever performed and one sold for $402 and the other for $399. They “claim” to be working, but who really knows! In the month prior to when mine sold there was one with no description other than “Seems to be working” and some good pictures that sold for > $600. That was actually the motivation for me selling my 339A. I now have two Amber 3501’s and the 339A was only being used occasionally for the oscillator. It takes up a lot of shelf space so I decided to sell it while the auction prices seemed reasonable for them.
The reason my 339A pulled a higher auction price than most of the others at the time has more to do with the auction itself. I’ve been selling on Ebay for about 17 years now and I know what it takes to get top $$ for my auctions. Typically when I go and look at the completed auctions for an item I sold on Ebay I expect mine to be the highest or within the top 2 or 3 in pricing of sold items. I’m still scratching my head as to how that 339A sold the month prior to mine at a price so much higher than mine, oh well, you win some, you lose some! Most people think that they can get away with a two sentence auction description and a couple of fuzzy pictures and get a great price on their auction, usually that’s not going to happen. You’ll notice my auction had a lot of detail, description of functional tests performed and pictures of said tests. This is what it takes to get big $$$ for your auction. In my opinion the DIYAUDIO mods I performed probably hurt the value of that auction, not helped it. I was actually disappointed with the price I got on that auction.
I sold my 334A a couple of years back, it was in mediocre cosmetic condition, but it passed (and exceeded) all of its tests with flying colors and worked great. It was also completely original. I had the same type of auction with test details and pictures. It sold for about $215 + shipping, which if you watch those auctions you’ll know is about the top dollar for that piece of gear. Most sell for $100 - 150.
In the end, I’m no Tim Rawson or Chinese conglomerate. I’m not out to profit or build a company off the backs of others IP. I do try and contribute what I can to this forum and I expect that at times the things I create from my time here may be sold and occasionally that may increase the value of the item. I would think we’d all be happy about that because if mine is worth more money then yours probably is too, if you sell it properly…..
Just an FYI,
I paid about $200 shipped for that 339A in “unknown” condition. I probably paid another $40 – 50 for the parts and pieces I put into the unit counting shipping and tax into the mix. A couple of knobs were broken and I had to source some replacements. I also had at a minimum 12 hours or more involved with the unit between recapping the power supply, hand cleaning all of the switch wafers and then performing the diyaudio mods. Remember that after selling anything on Ebay they keep 10% and Paypal another 3% of the auction total.
Add that up and factor in the hours of labor! If anyone really thinks that’s a profitable enterprise I’ve got to wonder what you do for a living. If I had sold it for $900 then I might see where you could complain.
Anyway, there’s currently two HP 339A’s in the Ebay completed auctions listings right now with NO mods and NO maintenance or testing whatsoever performed and one sold for $402 and the other for $399. They “claim” to be working, but who really knows! In the month prior to when mine sold there was one with no description other than “Seems to be working” and some good pictures that sold for > $600. That was actually the motivation for me selling my 339A. I now have two Amber 3501’s and the 339A was only being used occasionally for the oscillator. It takes up a lot of shelf space so I decided to sell it while the auction prices seemed reasonable for them.
The reason my 339A pulled a higher auction price than most of the others at the time has more to do with the auction itself. I’ve been selling on Ebay for about 17 years now and I know what it takes to get top $$ for my auctions. Typically when I go and look at the completed auctions for an item I sold on Ebay I expect mine to be the highest or within the top 2 or 3 in pricing of sold items. I’m still scratching my head as to how that 339A sold the month prior to mine at a price so much higher than mine, oh well, you win some, you lose some! Most people think that they can get away with a two sentence auction description and a couple of fuzzy pictures and get a great price on their auction, usually that’s not going to happen. You’ll notice my auction had a lot of detail, description of functional tests performed and pictures of said tests. This is what it takes to get big $$$ for your auction. In my opinion the DIYAUDIO mods I performed probably hurt the value of that auction, not helped it. I was actually disappointed with the price I got on that auction.
I sold my 334A a couple of years back, it was in mediocre cosmetic condition, but it passed (and exceeded) all of its tests with flying colors and worked great. It was also completely original. I had the same type of auction with test details and pictures. It sold for about $215 + shipping, which if you watch those auctions you’ll know is about the top dollar for that piece of gear. Most sell for $100 - 150.
In the end, I’m no Tim Rawson or Chinese conglomerate. I’m not out to profit or build a company off the backs of others IP. I do try and contribute what I can to this forum and I expect that at times the things I create from my time here may be sold and occasionally that may increase the value of the item. I would think we’d all be happy about that because if mine is worth more money then yours probably is too, if you sell it properly…..
I'm impressed that you can get decent prices on eBay. Usually the high cost of shipping the stuff I want to move on makes it a nonstarter. Maybe the prices have gone up enough that the effort may be worthwhile. Good presentation will make a difference.
I think anyone who can mod and sell one of these really vintage instruments for any price deserves all he can get. The cost and overhead is so high that it will never be profit making. I'm happy to see the stuff rescued from the recycle bin.
I think anyone who can mod and sell one of these really vintage instruments for any price deserves all he can get. The cost and overhead is so high that it will never be profit making. I'm happy to see the stuff rescued from the recycle bin.
HP339A oscillator improvement
http://www.diyaudio.com/forums/attachment.php?attachmentid=691878&d=1531612896
http://www.diyaudio.com/forums/attachment.php?attachmentid=691878&d=1531612896
This does sound like a good DIY project. When you mention the low pass filter on the osc output, are you saying it's on the U1 output right by the socket? or attached through the osc output jacks on the front panel?If that isn't good enoughYou can add a passive low-pass filter on the osc output. There are several sources for such... like Allen Avionics.
That will further attenuate the harmonics.
In fact that might make another good design DIY project.
THx-RNMarsh
What would be a target range for the low pass filter?
Cheers,
Hi everyone,
I just managed to post a link to an uploaded schematic --- I think. Is it infact accessible/ legible? My intent was to ask for confirmation that I understand the recommended mods. Obviously, I'm a newbie and am staggering around the facilities.
I'm going to try sending a second drawing describing the output buffer.
Be prepared for more ineptitude....
I'm Steve, BTW.
Hi again,
Another attempt.
View attachment HP339A OSC Out 1.pdf
View attachment HP339A OSC 2.pdf
This feels better. I hope it is.
Have I captured the recipe accurately?
As I mentioned to Sync, I applaud your efforts to turn all this old equipment into real Hot Rods!
I just managed to post a link to an uploaded schematic --- I think. Is it infact accessible/ legible? My intent was to ask for confirmation that I understand the recommended mods. Obviously, I'm a newbie and am staggering around the facilities.
I'm going to try sending a second drawing describing the output buffer.
Be prepared for more ineptitude....
I'm Steve, BTW.
Hi again,
Another attempt.
View attachment HP339A OSC Out 1.pdf
View attachment HP339A OSC 2.pdf
This feels better. I hope it is.
Have I captured the recipe accurately?
As I mentioned to Sync, I applaud your efforts to turn all this old equipment into real Hot Rods!
No problem. I bought several in various conditions but when they were dirt cheap. Now with some demand - too much IMO. But 100-150 for stock one is a good price range. I would like to know where you sourced replacement knobs. Most of them at their age are broken.
THx-Richard
BTW, Davada
CR14 hanging on the osc output -- a X1 buffer before it might reduce thd further ??? Have you tried that? may or may not make a difference (5.1Meg in series). but at -100dbv, everything matters.[I cannot try it because I am in Bangkok for another month and don't have a 339 to play with.]
THx-Richard
BSST, that is one way to attach images to the your post. Another way, after you press the QUOTE button to reply to a post and after you typed all the stuff you want, before pressing the SUBMIT REPLY button,
Scroll down the "Additional Options" box and press MANAGE ATTACHMENTS button.
Then select up to ten (I think) images to append at the end of your
post. I'll try it and post it below. The image is handy and create a small preview as shown below.
BTW, Davada
THx-Richard
Now that is interesting.
If I recall correctly, in something HP wrote, CR14 perhaps was causing (or a zener pair) was causing distortion and HP recommended using a higher value part. Prior to CR14, HPhad a circuit of other stuff in there and they changed it to the Resistor series w/Diode combo.
Then, are you suggesting an X1 buffer before the CR14 and the U3 change to LME4970? Now, maybe it was the CR11, CR13 zeners that were to change from 12.1 to 15.3v. I'll have to find the correct reference to it.
Finally, I always wondered about that dual 5Meg Switched Pot. If I could find one, I'd install it and see if it make a difference! I think we'd find some slightly better numbers with it as opposed to the old AB carbon comp pot. Like Davada found when he changed the 10K pot.
This is a stacked dual 5 Meg pot with a switch in it. I think it is the small 2 mm shaft like the bournes 10 K pot. Also, there is room enough for a standard sided pot body, instead of the mini square body this one is made from.
Richard while your over there, can you find a supplier that will provide 5 samples for testing of multiple HP339A untis to see if they will reduce distortion further?
Cheers,
Attachments
Finally, I always wondered about that dual 5Meg Switched Pot. If I could find one, I'd install it and see if it make a difference! I think we'd find some slightly better numbers with it as opposed to the old AB carbon comp pot. Like Davada found when he changed the 10K pot.
This is a stacked dual 5 Meg pot with a switch in it. I think it is the small 2 mm shaft like the bournes 10 K pot. Also, there is room enough for a standard sided pot body, instead of the mini square body this one is made from.
Richard while your over there, can you find a supplier that will provide 5 samples of the dual 5Meg switched pot for testing of multiple HP339A untis to see if they will reduce distortion further?
If not Richard maybe Davada, or someone else can find samples that we could test and see if it works?
Just thinking out loud here....
Cheers,
This is a stacked dual 5 Meg pot with a switch in it. I think it is the small 2 mm shaft like the bournes 10 K pot. Also, there is room enough for a standard sided pot body, instead of the mini square body this one is made from.
Richard while your over there, can you find a supplier that will provide 5 samples of the dual 5Meg switched pot for testing of multiple HP339A untis to see if they will reduce distortion further?
If not Richard maybe Davada, or someone else can find samples that we could test and see if it works?
Just thinking out loud here....
Cheers,
No problem. I bought several in various conditions but when they were dirt cheap. Now with some demand - too much IMO. But 100-150 for stock one is a good price range. I would like to know where you sourced replacement knobs. Most of them at their age are broken.
THx-Richard
BTW, Davada
[I cannot try it because I am in Bangkok for another month and don't have a 339 to play with.]
THx-Richard
Tried this. Did make any difference.
Hi Richard,
The 100 - 150 pricing I referenced was in regards to an example I gave of an older HP 334A I sold. I think you may have confused that with the 339A auction info.
The knobs can be sourced through Ebay as well, you have to be patient and constantly monitoring though. Sometimes they show up but are ungodly expensive like $25 - 30 for a single knob, so you just have to pass. Then there's times that they show up at a really cheap price and they're gone quickly, like < 24hrs. So it really takes a determined effort to find them. Another option, one of the knobs I replaced I bought a replacement wing style knob and transferred the original skirt which was still in decent condition.