Greetings all. Sometime lurker, first-time poster, utter n00b. Per title, my beloved Aleph 3 is somewhat poorly:
Plainly the reservoir caps have gone to the great part store in the sky. (Assuming this to be an age-related failure unless someone knows different? They have been shut in a hot metal box for the last 25+ years.) My soldering skills currently extend to knowing that you hold the cold end, but I'd like to have a shot at fixing it. (I plan to watch some Youtube tutorials for technique.) I have perused this previous thread on the subject, and have downloaded the service manual/schematic, to I've (hopefully) got a rough idea of what's involved, but all help and suggestions much appreciated. Specific current queries:
1. I have access to a basic 58W soldering iron - based on the previous discussion, ought to be powerful enough to desolder the big caps? May need to get a bigger tip - a solder sucker and desoldering braid, some 0.8mm cored solder, probably some flux kicking around somewhere, and a multimeter. There's sundry tweezers and and probably a set of helping hands about, too. Anything else I need?
2. For replacements these Rubycons seem to be a good option; 33KuF, plus higher temperature rating. Could alternatively go for Nichicons in 22KuF (105°C), or Cornell-Dubilier in 33KuF (85°C), based on what's readily available. Any opinions?
3. Per previous suggestion, replace C101, C102 and C103 with 470uF 63V Elna Silmics, plus 100nf MKB bypass (Voltage? Makes?) on C101 and C103. Think I've got that right?
4. I'm assuming this film cap (?) wants replacing as well, but I can't seem to find it on the schematic:
Any ideas? Like for like replacement, or something else?
5. Desolder, clean up and reinstall the thermistors?
6. Reflow solder joints: all of them?
7. Rough plan of attack: take loads of photos and label everything. Desolder all the wires leading to the PSU board from above. (The white ones plus signal grounds.) Hoping this will allow me to flip the PSU board over to access the bottom. (May unbolt the chassis uprights for better access.) Tasks as above, paying close attention to cap polarity. (Plus AN Others that I've missed?) Reassembly is the reverse of removal, as the Haynes manual always lies. Flick switch and pray. Assuming the smoke stays in the wires, check bias. Enjoy sonic goodness. What have I missed/at what point will I electrocute myself/burn the house down? (Some adult supervision is available.)
8. Not essential, but there's cap gloop all over the inside of the chassis; good means of cleaning this off?
Many thanks in advance!
Ben
Plainly the reservoir caps have gone to the great part store in the sky. (Assuming this to be an age-related failure unless someone knows different? They have been shut in a hot metal box for the last 25+ years.) My soldering skills currently extend to knowing that you hold the cold end, but I'd like to have a shot at fixing it. (I plan to watch some Youtube tutorials for technique.) I have perused this previous thread on the subject, and have downloaded the service manual/schematic, to I've (hopefully) got a rough idea of what's involved, but all help and suggestions much appreciated. Specific current queries:
1. I have access to a basic 58W soldering iron - based on the previous discussion, ought to be powerful enough to desolder the big caps? May need to get a bigger tip - a solder sucker and desoldering braid, some 0.8mm cored solder, probably some flux kicking around somewhere, and a multimeter. There's sundry tweezers and and probably a set of helping hands about, too. Anything else I need?
2. For replacements these Rubycons seem to be a good option; 33KuF, plus higher temperature rating. Could alternatively go for Nichicons in 22KuF (105°C), or Cornell-Dubilier in 33KuF (85°C), based on what's readily available. Any opinions?
3. Per previous suggestion, replace C101, C102 and C103 with 470uF 63V Elna Silmics, plus 100nf MKB bypass (Voltage? Makes?) on C101 and C103. Think I've got that right?
4. I'm assuming this film cap (?) wants replacing as well, but I can't seem to find it on the schematic:
Any ideas? Like for like replacement, or something else?
5. Desolder, clean up and reinstall the thermistors?
6. Reflow solder joints: all of them?
7. Rough plan of attack: take loads of photos and label everything. Desolder all the wires leading to the PSU board from above. (The white ones plus signal grounds.) Hoping this will allow me to flip the PSU board over to access the bottom. (May unbolt the chassis uprights for better access.) Tasks as above, paying close attention to cap polarity. (Plus AN Others that I've missed?) Reassembly is the reverse of removal, as the Haynes manual always lies. Flick switch and pray. Assuming the smoke stays in the wires, check bias. Enjoy sonic goodness. What have I missed/at what point will I electrocute myself/burn the house down? (Some adult supervision is available.)
8. Not essential, but there's cap gloop all over the inside of the chassis; good means of cleaning this off?
Many thanks in advance!
Ben
Snap in capacitors can be tricky to desolder without damaging the pads or plated holes. Honestly for something like that I would get a second iron of similar wattage and a helper. Heat up both legs simultaneously and quickly wiggle the cap out. Then you can easily remove the excess solder and give the boards a good cleaning with alcohol.
That looks like it was recovered from the bottom of the local harbor.
One of the most compelling cases against using 25V electrolytic capacitors with +/– 24V rails that I have seen.
Yes, take pictures, then disassemble and carefully clean everything with alcohol. You may want to wear nitrile gloves while doing this. De-soldering braid and a solder sucker will be necessary. Maybe a fresh tip for your iron as well. Read up on correct soldering technique. Buy fresh 63/37 rosin core solder. Obviously all electrolytic caps must be replaced. Recommend 22,000 uF, 35V for the main bank.
This is going to be a lot of work. Give yourself plenty of time.
One of the most compelling cases against using 25V electrolytic capacitors with +/– 24V rails that I have seen.
Yes, take pictures, then disassemble and carefully clean everything with alcohol. You may want to wear nitrile gloves while doing this. De-soldering braid and a solder sucker will be necessary. Maybe a fresh tip for your iron as well. Read up on correct soldering technique. Buy fresh 63/37 rosin core solder. Obviously all electrolytic caps must be replaced. Recommend 22,000 uF, 35V for the main bank.
This is going to be a lot of work. Give yourself plenty of time.
My thoughts exactly.
Unless the damage was done by water entry, the goo that the capacitors are covered in is dried electrolyte residue. That electrolyte used to be inside the capacitors. It's pretty corrosive (and probably toxic) stuff.
You will need to de-solder all the capacitors. Take pictures beforehand so you can get the replacement capacitors installed with the correct polarity.
As others have pointed out already, de-soldering snap-in capacitors is tricky but it is doable. One approach is to heat up one pin at a time. With heat applied bend the capacitor towards the other pin. Then repeat for the other pin. This allows you to wiggle the cap out of the board. That said, this approach can pull the through plating out of the board. This means you no longer have a connection between the top and bottom PCB layer (and any internal layers in a multi-layer board) which can be problematic.
A better approach would be to use a soldering iron with a very wide (10-12 mm) tip so you can heat up both pins at once. Have a helper pull the cap out once the solder is molten.
Once the capacitors have been removed you need to remove all traces of that electrolyte from the circuit board. I haven't found a good solvent for that yet but maybe others have. If you leave the electrolyte on the board, it'll continue to corrode traces and vias and result in failure not long from now.
Then clean up the capacitor footprints. Remove old solder. Add new solder. Remove that too. Then install new capacitors and clean up the flux residue.
With 24 V rails, I'd go for a 35-50 V rated cap if you can find one that fits. Given the Class A design and heat dissipation it'd be worthwhile to pay a bit extra to get long-life caps. Say 10k hours @ 85 ºC or several thousand hours at 105 ºC.
I wouldn't blindly start reflowing solder joints unless they look suspect. Ain't broken. Don't fix.
Another option would be to see if you can source a power supply board elsewhere (perhaps from Pass).
Tom
I haven't seen one like that before, odd to leak out the top. If you can send it to the factory we will fix it up for you. The .22uF cap is across the line and doesn't go bad.
I had a stash of proper 105 C to repair those at the factory. It isn't difficult to do just takes some care.
I had a stash of proper 105 C to repair those at the factory. It isn't difficult to do just takes some care.
Thanks all for the replies.
I'm in the UK, so unfortunately sending it to the factory isn't really practical. I have found a reputable repair shop who are prepared to take a look at it, but thought it would be good to try to learn a new skill.
@tomchr
This bit concerns me. The spillage isn't limited to the psu board; it's everywhere. And looks pretty well baked on to boot. Anyone else with suggestions for cleaning it off?
Replacement-wise it seems from what's available I can have higher temperature or higher voltage. Diameter is also a limiting factor; anything greater than the existing 30mm isn't going to fit.
I'm in the UK, so unfortunately sending it to the factory isn't really practical. I have found a reputable repair shop who are prepared to take a look at it, but thought it would be good to try to learn a new skill.
@tomchr
This bit concerns me. The spillage isn't limited to the psu board; it's everywhere. And looks pretty well baked on to boot. Anyone else with suggestions for cleaning it off?
Replacement-wise it seems from what's available I can have higher temperature or higher voltage. Diameter is also a limiting factor; anything greater than the existing 30mm isn't going to fit.
In general I like the idea of more capacitance and using up the available space. But with the way the Alephs are tightly packaged I would be looking at ways of cooling it down, like a new cover or lowering the bias a bit.
But right now is a REALLY BAD time to be shopping for parts, so for now with our help just focus on disassembling the ENTIRE amp for a nice cleaning....?
Try alcohol or mineral spirits first.
But right now is a REALLY BAD time to be shopping for parts, so for now with our help just focus on disassembling the ENTIRE amp for a nice cleaning....?
Try alcohol or mineral spirits first.
For cleaning, you could start with distilled white vinegar, then finish with isopropyl (rubbing) alcohol. Both contain water, so you have a neutralizing solvent to work on the dried electrolyte. As I mentioned earlier, best to wear gloves while cleaning. Another solvent to try is Naptha or lighter fluid, which is basically the same thing.
All of these solvents are safe to work with. It is the electrolyte that can be somewhat corrosive.
All of these solvents are safe to work with. It is the electrolyte that can be somewhat corrosive.
damn knowitallers (xcept Wayne, he really Knows All, and Then Some)
.......... no one to tackle that list1. 58W , but with big tip, cranked to max temp ( if there is regulation) ; bit tip means something massive, not tiny sharp end tips ...... say that 3mm wide chisel at tip end is minimum needed , more the merrier
2. more uF yes, more C Oh Yes!; if you can't get both , go with Oh Yes!; if Pa did put 25V on 22V5 rails, don't listen to Chickens (ZM usually being Biggest One) fearing of 25V caps; though, if you can squeeze 35V ones there, another one more the merrier
3. yes, replace small ones too; bypass is welcome; use ones which pleases your eyes most
4. Wayne did tell tiny one is OK
5. disassemble it carefully, starting first with wire bridges leading to output pcbs; orient cap pcb to suits you; clean solder iron, first add some fresh solder to each cap pad, it'll help immensely for fast and efficient removal of each cap end; heat one cap pad, no more than few secs after you see it melted , try to lift that end of cap (lean its top to other pad side); leave it - move to other cap pad, repeat; now both pins are mm or so away of pcb; repeat procedure with first, then second then first then second cap pin, until you get it out; crucial is to limit heating of each pad to minimum time, and pads will survive; solder sucker afterwards is piece of cake, to get pads clean
6.no need if you see them decent, but cleaning of entire pcb is a must; everything what Boyz already told, I'm often using 70% alcohol, don't know exactly which one, don't care and don't bother
7. yes, photos; I did cover some in No. 5 ; smoke will stay in, hopefully - just use simple and trusty logic and sense for tidiness
8. see up
9. check torque of all OS mosfets; use either torque screwdriver (0,9Nm) or end of sentence n No.7
10. OPLDF is , as always, your last and most trusty solution
Classic e-caps are damp with water, ethylene glycol, and borax electrolyte. This form of glycol is notorious for poisoning cats and dogs who find spilled anti-freeze. You have to lick a fair amount to get real sick. The boric acid is nasty on the tongue so I doubt you would lick much. These alone encourage corrosion so "other stuff" is added. Three I looked-up were very mildly toxic, you would have to make a meal to get dead. One of them is also used as a recreational drug, go figure. A little makes you mellow, a little more makes you mellow forever.
So yeah. Treat with care, but it isn't thallium, tetra ethyl lead, or dimethylmercury. More like triple-strength vinegar. When fresh. The dried powder should be rinsed off the skin quickly, and not inhaled. But we have caterpillars almost as toxic.
I don't understand vinegar for cleaning cap-spew. The white smutz is likely boric acid, so another acid may do little?
We have some special soap for this but it is basically just soap. And yes don't clean acid with acid. Mild soap and stiff brush rinse and dry well maybe alcohol to help dry. For caps 25 Volt but higher temp and longer life. Higher voltage would be nice but you want capacity and long life. Zen Mod directions are very good.
Progress! Three boards out and cleaned. Wasn't having much joy with soap, so went straight to IPA, which in combination with a plastic razor blade is actually making fairly short work of it.
Before:
After:
Desoldering was a bit of a learning curve, but I'm getting better. (Repeats to self: "I must stop singeing my beard with the iron.") Still not quite nailed the solder sucker yet; more practice required with the timing. Things get trickier from here, as there are more and larger things to remove. I need to get labelling and annotate the schematic before I go any further.
Question: is this sort of thing what I'm after for the bypass caps?
I've also found that the insulation has split around the legs of one of the thermistors, so I'm thinking I'll replace that while I'm in there. A new one is only £1.50 or so.
Thanks for the help getting this far. @Logic800 appreciate the offer; Woodford Green is a bit of a way off, but if I get really stuck I'll be in touch.
Before:
After:
Desoldering was a bit of a learning curve, but I'm getting better. (Repeats to self: "I must stop singeing my beard with the iron.") Still not quite nailed the solder sucker yet; more practice required with the timing. Things get trickier from here, as there are more and larger things to remove. I need to get labelling and annotate the schematic before I go any further.
Question: is this sort of thing what I'm after for the bypass caps?
I've also found that the insulation has split around the legs of one of the thermistors, so I'm thinking I'll replace that while I'm in there. A new one is only £1.50 or so.
Thanks for the help getting this far. @Logic800 appreciate the offer; Woodford Green is a bit of a way off, but if I get really stuck I'll be in touch.