Tascam 488 Group 1 (tracks 1-5) not working


New member
I've recently adquired a Tascam 488.

What i saw first is that the preamp for the track 1 is not working properly, whenever i crank its volume all the way up i cant hear anything. However, the volume meter shows something if i have its volume all the way up, but it ain't the mic or instrument plugged in. My best guess is that it is noise. If i record something, it can be heard but wayyyyy too low.

What i tried is using track 2 (all the other tracks work in the mixer) assigning the record function to track 1. The meter shows the correct levels though when i playback what was recorded, the same thing happens in which the volume is wayyyy to low. This also happens with track 5

Having said that, i think that there is something wrong with group 1. I don't know if what is causing it is the thing with the preamp on track 1 (if i use the input on track 5 i can hear it normally through it though not its recording).

I need guidance as i have already opened a few portastudios but i have never dealt with this problem. I could give it to a technician but first i wanna know if i can do it myself

Well the question comes to if you can fix it yourself why the question? This is not to say you can not do it but that the question indicates you are not taking the proper steps to diagnose what is really happening. In my case I would place a 1 KHz -10dBV signal in the line in and see what comes out the monitor or buss out section. Sometimes things are as easy as the slide switches needing cleaning and maybe a master module having some resoldering done to fix the low grade of manufacture. A Technician will start the trace with schematic in hand and go from line in to line amplifiers to busses and then down to the recording section.
I tell clients to clean and inspect the heads first before bringing it in. One 34 deck came in with clean heads and as I looked at them I asked what he used and of course it was Isopropyl again which is pretty much worthless. The heads had to be cleaned with Acetone being the residue was allowed to pile up for so long and did I mention that Isolpropyl is worthless for this- want to make sure you understand it as many still use it. Do you have Deoxit D5 for the switches? Denatured should be used on heads as a minimum and Acetone (Lacquer thinner) as a secondary cleaned- keep it confined to the swab as it will melt plastic. I have fixed these here in my shop in the past many times.


New member
I have tried with isopropyl but not with deoxit. Something i missed in my explanation is that i played a cassette which had something recorded in track 1 (with a 4 track) and reproduced it with no problem. If i have to solder something i need guidance as i can solder with ease but i'm lost with the board of this machine
Well it works like this- If you want to become a Technician and do the work he can do then it takes time training and school not to mention getting a good amount of experience. If you do not want to become a Technician then it is better to just have one do the deck for you as the $1500 or more of equipment and test tapes involved will still not give you the experience to fix these and so then you are back to square one. I assist 9 guys through E mail but they have to have the basic tools and knowledge to use scopes and meters. To trace a missing signal one normally does so with a Oscilloscope. They used to be $2000 but some Rigol units that are TFT display devices might suffice at $300 or so. Test tapes can be had from Genn Lab but again these are not cheap- probably at least $100 US now days if not more. Then you need a good service manual. I get paper ones from Stereomanuals.com where I just got a 688 SM from him. They are not cheap or free but the best for working on this stuff. Even as a 46 year Technician in this field working from poorly scanned or cut up Pdf schematics wastes a lot of time and make it even more difficult for the beginner. This may sound like bad news or good depending on your age and where you want to go from here. I can tell you that as business fail due to the Pandemic my business has gotten even more busy and I already have too much work. That is why we need new guys to do this work. Gerhard a trainee of mine has already started working on decks like this in FL and has been very successful. He trained for about 7 months but he is not starting from ground zero like some guys are. These are realities as I know them just to make you aware- I tell people all the time there is no magic wand- you need to do the same as a Technician will do. This is true no matter how you receive it.
The tracks on the cassette tape are extremely critical and the edge tracks are the most damage or worn in this format. This is why it is often necessary to use a new fresh tape to test these decks. As the tape wears the edges curl inward and away from the head- this results in poor levels and lack of high end. it is a tape to head contact issue really. A new fresh tape if you look at the surface looks like it is flat or even the edges look cut upward and I think they knew about this and slit the tape like that on purpose. All the tape can come from 26-30" web or master rolls I have been told. They do not make Chrome tape anymore so being that these deck USE only Chrome tape, it might be good to secure a good supply of Maxell XL II C-90 tapes. Not used one but fresh.
Usually in my experience when someone say the record groups are not working they mean the Tact switches are not arming the channel. They need to be changed out- new ones work great. Old ones can maybe be cleaned but it doe snot last long. So did you fix the problem yet?