Recapping Monitor PCB in a Tascam 388

38869420

Member
So the link on tapeop to Sweetbeats recap thread is dead and I’m looking to recap the audio cards and monitor pcb of my 388

I’ve got a mouser list for the audio cards but wondering how to figure out what needs to be replaced on the Monitor PCB.

ive never recapped anything before so I’m keen to practice on some other less valuable stuff first but any tips and guidance would be appreciated.
 

ecc83

Well-known member
I would not like for one moment to step on the toes of The Legend that is Sweetbeats on analogue so this is just my personal observation about audio circuit work in general.

My first question is, as always, "why re cap?" Since the mixer is about 35yrs old, maybe academic in this case however I will venture my next point. MEASURE the fekker first! That is at least do a voltage table and a gain check and if at all possible check the LF turnover frequency. Doing that means you then have some numbers to ensure your work has not buggered anything.

Practical matters: Use a good quality temperature controlled iron of about 50W rating. Good quality 60/40 Lead solder because that is what is there. I would start by cleaning the PCB with meths and a stiff brush. Flood each capacitor joint with a little fresh solder then IMO use solder wick to remove solder. Some folks swear by the "click-clunk suckers" I swear at them, had them lift print. You will need a LOT of solder wick.

I would NOT increase the values of any of the caps unless Mr S says so.

Tip. If you go to a radio repair shop (if you can find one!) you should be able to blag a video PCB or similar from the scrap bin to practice on. Or the local recycling site.

Dave.
 

sweetbeats

Reel deep thoughts...
I agree with much of what Dave said in principle, though I hate solder wick. Now, bear in mind Dave likely works on stuff with larger traces and larger solder joints more frequently than I do. Manual vacuum solder suckers can be a bit tedious there if there is a lot of solder to pull. I don’t work on any tube gear or vintage amps and such. Anyway...

are you considering recapping your faulty monitor PCB? I really, really doubt your electrolytic caps have anything to do with your problem. I meant to comment on your other thread but I’ve been monumentally busy. If I was going to make a guess I’d bet the 4000 series logic chips are to blame. I don’t have the manual in front of me...U301 and U302? 4011 parts? Cheap and available. There have been other issues with the very limited selection of 4000 series parts on the 388, so I’d shotgun those if I was going to just shotgun something. Those logic chips accomplish analog switching and work in conjunction with transistors to auto-switch the signal path depending on modes. When they go bad weird stuff happens. If you’re bent on recapping just use the same voltage/value parts, and any modern low ESR parts are good here. You could replace all with Nichicon PW or the like.

can you tell me more about the link that’s broken? I’m not even sure I know what thread you’re talking about on tape op. I’d like to see if it’s something I can fix on my end.
 

38869420

Member
Thanks for the replies & guidance, I appreciate it.

I'm learning as I go with maintaining this stuff as there's no techs in Tasmania and I figure I should learn how to upkeep this stuff.
My first question is, as always, "why re cap?" Since the mixer is about 35yrs old, maybe academic in this case however I will venture my next point. MEASURE the fekker first! That is at least do a voltage table and a gain check and if at all possible check the LF turnover frequency. Doing that means you then have some numbers to ensure your work has not buggered anything.

Well, just off recommendations really, and because I have a spare machine I thought 'why not learn...' as it'll probably need to happen anyway. I've inspected the cards though and from looking, all the caps look fine so your advice of measuring it first is sound. It would need to be powered to measure everything, correct?

My spares machine has a host of problems, but now my main machine is rock solid again, I can worry about trying to make the second one operational but my first priority is trying to fix this 8200 / 16400Hz tone in the Monitor PCB I swapped out.

@sweetbeats Yeah, considering
Practical matters: Use a good quality temperature controlled iron of about 50W rating. Good quality 60/40 Lead solder because that is what is there. I would start by cleaning the PCB with meths and a stiff brush. Flood each capacitor joint with a little fresh solder then IMO use solder wick to remove solder. Some folks swear by the "click-clunk suckers" I swear at them, had them lift print. You will need a LOT of solder wick.

I've got a good soldering iron with temp control, was considering getting a desoldering gun. Would this be overkill? I've got an MPC 3000 i'm going to have to replace a bunch of Tact switches on soon and will always need to do little jobs here and there so figure it's a decent investment.

are you considering recapping your faulty monitor PCB? I really, really doubt your electrolytic caps have anything to do with your problem. I meant to comment on your other thread but I’ve been monumentally busy. If I was going to make a guess I’d bet the 4000 series logic chips are to blame. I don’t have the manual in front of me...U301 and U302? 4011 parts? Cheap and available. There have been other issues with the very limited selection of 4000 series parts on the 388, so I’d shotgun those if I was going to just shotgun something. Those logic chips accomplish analog switching and work in conjunction with transistors to auto-switch the signal path depending on modes. When they go bad weird stuff happens. If you’re bent on recapping just use the same voltage/value parts, and any modern low ESR parts are good here. You could replace all with Nichicon PW or the like.
Thanks for that, yeah trying to get rid of this high pitch tone and figured i'd start with the Caps. Was pretty noisy generally in hindsight now i've swapped to a good Monitor PCB.

Yeah there's a U301 & U302 in the parts list IC, MC14011BCP. Would this be a replacement? https://tinyurl.com/5benyjbe there's no stock on Mouser or RS. Happy to just do that for now and see how I go. I'm happy with doing as little as possible really, then keep troubleshooting other problems, but would love to do as much as possible sooner or later to increase the working life of these machines.

can you tell me more about the link that’s broken? I’m not even sure I know what thread you’re talking about on tape op. I’d like to see if it’s something I can fix on my end.
Yeah, its in the big Tape Op 388 thread here - https://messageboard.tapeop.com/viewtopic.php?t=76869 the link is for "Tascam 388 refurb and recap thread:"Sweetbeats" numerous pictures of the process." http://homerecording.com/bbs/showthread.php?t=286434
there's a bunch of Home Recording threads of yours that go to dead links now. I've been meaning to collate a lot of this online info into some kind of extra manual.
 

ecc83

Well-known member
FWIW a vacuum desoldering gun has been a lifesaver for me. It's made desoldering chips infinitely easier.
Ah, there are several sorts. The 'pro' job is a vacuum pump permanently sucking through a tube next to the job. The other is a spring powered 'bike pump' that gives one 'suck' at a time. I would never use the latter on delicate print.

Wick does need some practice NEVER lift it cold.

Dave.
 

jpmorris

Tape Wolf
Ah, there are several sorts. The 'pro' job is a vacuum pump permanently sucking through a tube next to the job. The other is a spring powered 'bike pump' that gives one 'suck' at a time. I would never use the latter on delicate print.
Yeah, the 'pro' ones with a continuous or trigger-operated electric pump have become quite cheap lately. When I was first looking, you could only get the Hakko ones and they were about £600 or so. Now there's a bunch of cheap ones like the Anesty AZ-915 which is perfectly good for this kind of thing.
 

sweetbeats

Reel deep thoughts...
That MC14011 part you linked is probably fine. Me personally I pay a little more to get, like, a genuine TI part from someplace like Mouser for better assurance it’s a genuine part, and better quality. BTW you probably had a harder time finding options because Motorola added the “1” in front of the part number. So their derivation of the 4011 part is 14011, but it’s just a “4011” 4000 series CMOS part. Very common and still in production. But not so common if you are trying to find the specific Motorola part, long out of production.

Here:

https://www.mouser.com/ProductDetail/Texas-Instruments/CD4011UBE?qs=VuX40u8tcuBeHmo5eBP4YQ==

The link to my threads are probably broken because HR.com migrated to a new platform recently. So the links will have to be updated on the tape op forum. I didn’t realize those links were there.
 

jpmorris

Tape Wolf
I’ve been looking at this one but there’s so many options I’m happy for any recommendations from real world use https://www.ebay.com.au/itm/ZD-915-...m-Gun-Sucker-Rework-Station-LCD/324146944561?
Yeah, I double-checked and that is the model I've been using for a couple of years now with no real problems. Opening up the gun for cleaning could be easier, but it's been reliable so far (touch wood).
The only time it's caused me a problem was when I reassembled the gun incorrectly after cleaning - I swapped the filter pad and metal plate around, which caused it to block the vacuum pump. Once I realised what was going wrong and swapped them around it was perfectly happy again.
 

38869420

Member
That MC14011 part you linked is probably fine. Me personally I pay a little more to get, like, a genuine TI part from someplace like Mouser for better assurance it’s a genuine part, and better quality. BTW you probably had a harder time finding options because Motorola added the “1” in front of the part number. So their derivation of the 4011 part is 14011, but it’s just a “4011” 4000 series CMOS part. Very common and still in production. But not so common if you are trying to find the specific Motorola part, long out of production.

Here:

https://www.mouser.com/ProductDetail/Texas-Instruments/CD4011UBE?qs=VuX40u8tcuBeHmo5eBP4YQ==

The link to my threads are probably broken because HR.com migrated to a new platform recently. So the links will have to be updated on the tape op forum. I didn’t realize those links were there.
Thanks for the rundown. Still not too sure on how to discern the differences, but slowly learning. Would this part work? Seems to be the same
Just those Mouser parts have a $35 shipping cost added for where I live. Same with the other options.
 

sweetbeats

Reel deep thoughts...
Okay. Understood on the Mouser parts. Those last ones you linked appear to be the same spec part, and in your case that eBay option you linked earlier may be just as good as the Jaycar option. So either one.
 

38869420

Member
Okay. Understood on the Mouser parts. Those last ones you linked appear to be the same spec part, and in your case that eBay option you linked earlier may be just as good as the Jaycar option. So either one.
Great thank you. Trying to get the parts through a more reputable local supplier but good to know those will work.
 
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