388 very quiet during stereo playback

R

rob388

New member
Hello my very first post!

I've just acquired a Tascam 388 with an issue maybe you could all help with.

When I go to listen to something I've just recorded I get good volume with the aux and eff buttons pressed in, but with the stereo button pressed I have to turn everything right up to get a barely audible signal.

Apologies if this sounds a little vague, I'm brand new to analogue and to be honest would like to learn as much as possible.

The only thing I've checked so far are the fuses and they're all good.

Very very happy to have stumbled upon the 388 here in the UK as there's not many about ?

Thanks all, hope you can help.
 
I don't know this machine, but looking at pictures of it, my guess would be that you haven't assigned any channels to the stereo bus.
See if you can find a scan of the manual, the mixer seems to work a bit differently to anything I've used before.
 
As far I know I have to press the L R button in the assign section of the track to get the track to come through the stereo bus. I've done this and with L R engaged I get a barely audible sound and without it engaged there's nothing.

Yes I do have the manual I'm gonna take a read now.

Thanks guys.
 
I'm using headphones, this was leading up to my next question about the correct leads to connect my Yamaha monitors with 1/4 inch jack inputs.

Any advice on this if possible would be great.
 
For my monitors I'm using a rca to 1/4" ts cable. RCA monitor out of the 388 to the 1/4" inputs of my monitors.
Are your monitors powered?
 
So with a source connected to an input channel, and with the trim knob and fader set to a nominal level, and the L-R assign button latched (in the down position), you can't hear anything in the headphones with STEREO as the source over in the monitor section?
 
Thanks for the info regarding the monitor cables, I'll order some this weekend.

Yes the monitors I have are powered, and I'm using some guitar I just recorded to channel 1.

Sweetbeats all that is correct except I can only hear a barely audible signal with stereo at the source in the monitor.

It's so quiet you almost have to push the earphones to your ears, so there's definatly some signal there just not very loud at all.
 
The repair first involves diagnostic work to determine what the problem is, and then if it is switching logic to determine which of the multiple parts are faulty. Once the faulty part(s) is/are identified it is a matter of replacing the faulty part(s).

You need a legible copy of the service manual, a good multimeter and test tone generator and to know how to use them, and you need to have some kind of decent desoldering tool and a good soldering iron and some skill in using these things. All the boards in the 388 except for the motherboards are phenolic resin as opposed to glass fiber. It's really easy to apply too much heat or for too long and have traces separate from the board. Then you are spending time trying to cobble connections back together and make repairs to the traces.

see this thread here:

https://homerecording.com/bbs/general-discussions/analog-recording-and-mixing-tape-and-gear/new-388-problem-390817/

One of famous beagle's issues was a bad switching chip.
 
sweetbeats said:
The repair first involves diagnostic work to determine what the problem is, and then if it is switching logic to determine which of the multiple parts are faulty. Once the faulty part(s) is/are identified it is a matter of replacing the faulty part(s).

You need a legible copy of the service manual, a good multimeter and test tone generator and to know how to use them, and you need to have some kind of decent desoldering tool and a good soldering iron and some skill in using these things. All the boards in the 388 except for the motherboards are phenolic resin as opposed to glass fiber. It's really easy to apply too much heat or for too long and have traces separate from the board. Then you are spending time trying to cobble connections back together and make repairs to the traces.

see this thread here:

https://homerecording.com/bbs/general-discussions/analog-recording-and-mixing-tape-and-gear/new-388-problem-390817/

One of famous beagle's issues was a bad switching chip.
Click to expand...

Oh no! Here we go again! :)
 
Ah, yes. In that case it was a failed 14069 hex inverter. Note that there were some business involving the service manual giving the wrong chip number, hilarity ensued. Also the PCBs seem to be the phenolic ones, which are very delicate to work on and easily damaged by overheating the tracks. Until I got a desoldering gun with a vacuum pump I had terrible trouble desoldering ICs at all, though it is sometimes possible to cut the chip off the legs with sidecutters and so desolder them one pin at a time.
If you've never done soldering work before, a 14-pin IC is not the best place to start. In that case it might be worth looking for a service tech of some kind.
 
A couple of things.When the 4069 fails it locks the unit into either the monitor mod or the stereo mode.Verify all the L-R routing in the channel strips are un assigned.Monitor section work? The monitor section will work only if all the L-R assign buttons are up.It's also real easy to break the BUSS PCBs when removing them.
 
Thanks for the info everyone, I've currently removed all the pcb's for channels 1-8 and cleaned all the pots and faders I'm gonna continue with the other pcb's in the mixer section tomorrow as I've run out of switch cleaner.

I was going to do this any way regardless of the stereo playback fault as there are a couple of crackly pots.

Which board is the 4069 hex inverter chip on?

I have the manual for the Tascam I'm gonna have a read up tonight.

I've used a signal generator and oscilloscope many years ago and have a very very basic knowledge of electronics.

It looks a bit daunting at the moment, many wires many chips and many boards!

Would it be wise to pull every single connector and clean?

What else can I do while stuff is apart?

I'll continue tomorrow and report back regarding the L R routing stuff.

Thanks again everyone, your help and advice is appreciated.
 
Stop.

No offense.

The best way to fix a problem is to focus on that problem, rather than do a whole bunch of stuff at once. The risk is you create more problems without knowing if they are old or new, related, unrelated...

The hex inverter is on the BUSS B PCB, but we don't even know if that is the cause of your problem yet...we don't even have an affirmative definition of your issue.

In an earlier post I indicated step 1 was to conduct diagnostic testing. So put the 388 back together, and check first to see if your original problem still exists, and determine if there are any new issues.

If the answers are yes and no respectively, then gather your multimeter and signal generator.
 
listen to Cory.

The worst disease when working on anything, be it a car or recorder, is "While-We're-At-It-Itis".

You end up with things taken apart, screws everywhere and it REDUCES the probability of it actually going back together working and intact.

But of course, I've never suffered from that disease....... :D
 
No offence taken.

I've got a bit carried away ?

I'll put her back together today.

Just to clarify, the signal generator I used years ago was box like machine that could generate square waves, saw tooth waves, sine waves and some others, we passed these signals through electronic circuits and measured how these waves were affected with a cathode ray oscilloscope.

I carefully read the 'another 388 problem' thread last night and from what I made out the tone generator was an app from a phone that could generate tones of different frequencies, is this correct?

I hope this is correct as I don't have a signal generator or oscilloscope, these were used on an electronics course I took many years ago. I've forgotten about 95 percent of what I learned so it would be fair to say that you guys are dealing with a complete novice, albeit a willing one!

I'll get everything back together today and report back.

How can I upload photos?

RFR I know what you mean!

Many thanks guys.
 
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