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Used Test Equipment Re Cap And Maintenance Advice
Posted by
EE54
on 26 Mar, 2024 11:09
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I have a list of instruments that I’m cleaning up and restoring
+ HP 53131A counter
+ TDS 694C 3 GHz scope
+ Anritsu MS2602A 8.5 GHz SA
+ Anritsu MG3602A signal gen
All of them are working but since I’m planning on selling some of these, I want to do some maintenance first. My plan is:
+ Re cap the PSU of the MG3602A and the 53131A due to how hot the sig gen psu gets and how old the counter smps is
+ Add heatsink to the 694C trigger ASICs and replace the NVRAMs with the ones that were designed in another thread.
Does this seem ok? I don’t want to overdo it and risk damaging already working instruments by unnecessarily tear them apart. Especially the Antitsu SA, it looks fairly complex and I don’t want to break an unobtainable board by shotgun recapping the whole thing.
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#1 Reply
Posted by
Paceguy
on 27 Mar, 2024 23:21
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I have lots of used test equipment, some of it I sell from time to time. If it's working properly, I don't see the need to make improvements. Personally, when I purchase used test equipment, I prefer to see that nothing has been changed and it's original as can be. That way, if something fails down the road, I can rule out the posibility that the previous owner(s) work was not the cause. That is just my own opinion. Others may beg to differ.
If you do go ahead with the improvements, it would be advisable that you advise the potenial buyer of the work you undertook.
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Personally I would much rather buy unmolested TE than TE that someone has attempted to repair or to recap. It's always questionable as to what their skill level is and what grade of components that they use.
PS I have several pieces of Anritsu gear and and have never had to recap any of it and over 100 pieces of HP gear and I have only replaced a couple of caps in it. IMO both Anristu and HP use very high grade caps and very good designs so cap failures are rare in them. I definitely DO NOT recommend replacing caps in HP and Anritsu gear wholesale. I think that you're more likely to cause problems than to fix any potential problem.
When I buy TE from Ebay, the FIRST thing that I look at is to see if the seals have been broken. If they have then I won't pay more than a scrap metal price for it because you can never tell what have been stolen out of it or what shoddy repairs have been done of what kind of of other damage may have been done to it.
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#3 Reply
Posted by
colorburst
on 28 Mar, 2024 10:46
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I find that preventative maintenance adds very little value to used equipment and sometimes is a negative even.
Many hobbyists prefer to do the work themselves. In fact, the late Jim Williams was said to pay more for broken equipment than working!
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#4 Reply
Posted by
TheDefpom
on 31 Mar, 2024 05:48
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As someone that tries to buy broken test gear to make videos about fixing them, I would much rather have something which hasn't been worked on before, or recapped, as it only raises questions about potential errors being made by the refurbisher.
Also as you intend to sell the units, recapping is going to eat into your profit big time, so unless something is actually having problems working, I recommend you leave them alone.
This is a bit hypocritical of me, as I do the exact opposite for the items I buy and may then sell on once fixed if it is not something I actually need, as I will re-cap them even if the caps test OK, just to be sure, but I do it for the video content and I usually expect to make nothing or maybe even a loss when selling the items on because of the cost to replace dozens of caps, often axial types, which cost a lot more.
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#5 Reply
Posted by
Swake
on 02 Apr, 2024 07:08
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I do not understand the systematic recap frenzy. In way too many cases it is a waste of time and resources.
On top of that many only look at the capacitance/voltage and forget about the other specs that might very well have been important, or not.
Not saying that caps never have to be replaced. There is a lot of crap out there. But then it is rarely worth going further than a simple repair.
Certain caps are known to be problematic. (Rifa, do you read this? No you don't. You even had to rebrand your stuff to mitigate for reputation damage).
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It's been a long time since I recapped something just for the hell of it or based on an assumption. I used to fall into that trap of recapping if anything was a bit out of spec, but a few thousand repairs into my career now I'm far less tempted. If there's no good reason to change them (visibly leaking, measuring bad or looking like they are headed that way, known problems with that batch, part is underrated for the job, etc) I tend to leave things alone now.
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#7 Reply
Posted by
fmashockie
on 07 Apr, 2024 13:44
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As someone who works in the repair industry (I am an in-house engineer for a biotech company) and also purchases used/broken lab/test equipment to repair and make videoes (similar to Defpom though not nearly as good
), I really don't understand the obession with recapping.
Preventative maintenance (PM) involves changing out parts that you can confidently predict when they will fail. You can somewhat accurately predict their lifespan. I like to use vehicle repair as an analogy - you preventatively replace your brakes (or you should!) before you are grinding metal on metal.
Capacitors do not make for a good PM replacement part. Why? Because you cannot accurately guess when they will fail. Some caps still test bang on after 50 years of use. Others fail within years. This is across cap manufacturers - good and bad.
My advice to you is, if the equipment works fine, leave it alone. Anyone who sees that you recapped it for the sake of doing so is going to likely pass it up for something is all original - even if the all original one it isn't working. Or at least I would.
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#8 Reply
Posted by
fmashockie
on 07 Apr, 2024 14:13
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Additional thought- if you are really interested in reselling these and increasing the purchase price, consider having these calibrated by an ISO-accredited lab. Depending on their resale value/equipment type, that could increase the price by hundreds or thousands of dollars. It also increases the diversity of prospective customers. Now you might have labs (in addition to hobbyists) interested in buying.
Recapping will likely open the door to negotiate lower prices - if you advertise it. And you should if you are a honest seller.
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#9 Reply
Posted by
fmashockie
on 07 Apr, 2024 14:26
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Many hobbyists prefer to do the work themselves. In fact, the late Jim Williams was said to pay more for broken equipment than working!
Wow if this is true, then I feel a bit less crazy for some of purchases I've made for broken equipment! For me, repairing this stuff is just as fun as using it.
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#10 Reply
Posted by
Zenith
on 07 Apr, 2024 19:40
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I think it depends on what it is. The capacitors in some equipment are notorious, Rifas, the 1000 µF 25 volt Cosonic capacitors in Hameg scopes, various capacitors in Tek 2400 series, so if you want to sell the item as working with some expectation it will stay working for some time after it was sold, change 'em.
I'm not in favour of shotgunning the lot. It's a waste of time and money.
As for the items mentioned by the OP, I'm not familiar with them. He must do his homework and if they have known problem caps, make a decision as to whether to do it. I can't see it makes sense to just do it.
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#11 Reply
Posted by
BrokenYugo
on 07 Apr, 2024 20:16
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I get shotgun recapping as a matter of policy with tube era stuff full of wax paper caps that are probably all some degree of bad by now. More modern gear, the more I work on it the less I want to mess with it, fix the problem/problem area and run it to the next failure, and hope the failure is also something repairable. My experience with putting in extra work like that is it just hurts that much more when it inevitably blows something that scraps the whole unit.
In my experience selling anything people buy on clean and functional above all else, "looks shiny and runs nicely" is what you should aim for, more meticulous people tend to pay less so there's little point in catering to them.
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#12 Reply
Posted by
jdragoset
on 07 Apr, 2024 20:46
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I think repairing the broken stuff is the reason for the purchase, as most wont resell for very much anyway.
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#13 Reply
Posted by
Zenith
on 07 Apr, 2024 21:25
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I think repairing the broken stuff is the reason for the purchase, as most wont resell for very much anyway.
It depends. A lot of people just want something like a sig gen or oscilloscope that works properly, with no dodgy switches or other obvious faults. Fixing one would be a nightmare for them.
I like fixing broken stuff, but I'm not willing to pay much for it.