Tascam M224 Mods

Cynosure

New member
I am picking up a Tascam M224 for a really good price because the seller took into consideration that I plan to service it to get it in good working order again. Can anyone help with a service manual or mods?

I read a post by the user Beck about replacing some of the opamps with OPA2604's. Can anyone point out which opamps I should replace? Or do I just replace every single JRC4560?

Also, I read about some issues with the power supply. That doesn't really make sense to me because the power supply either has enough current or it doesn't. Could it need larger filter caps? Would that help?

Beck also mentioned replacing the resistors. Does that really make much of a difference? My previous DIY experience is with synthesizers. With those, it is common to replace the caps but I have never heard of replacing the resistors before.

A service manual or schematic would really help a lot. Does anyone have a pdf that they can share?

Thanks for the help!
 
I am picking up a Tascam M224 for a really good price because the seller took into consideration that I plan to service it to get it in good working order again. Can anyone help with a service manual or mods?

I read a post by the user Beck about replacing some of the opamps with OPA2604's. Can anyone point out which opamps I should replace? Or do I just replace every single JRC4560?

Also, I read about some issues with the power supply. That doesn't really make sense to me because the power supply either has enough current or it doesn't. Could it need larger filter caps? Would that help?

Beck also mentioned replacing the resistors. Does that really make much of a difference? My previous DIY experience is with synthesizers. With those, it is common to replace the caps but I have never heard of replacing the resistors before.

A service manual or schematic would really help a lot. Does anyone have a pdf that they can share?

Thanks for the help!

I don't have a manual but if you want to do any mods you will have to take a few things into consideration......first and foremost, if the unit needs to be repaired you probably should do that first...

you mentioned the power supply....there might be issues there if the replacement op-amps will draw more current than the original ones.... also, the specs on the op-amps will probably be different and might not work to your expected satisfaction....could cause problems....electrolytic capacitors tend to lose their capacitance and develop ESR over time....and if they are bad should be replaced....resistors.....well metal film resistors are less noisy than carbon comp ones......but changing every single resistor with be very time consuming and expensive...but then again, it all depends what you are after....

and after completing a mod it might be best to then check the operation of the unit just in case you ended up making a mistake....not saying that you will but if you do a ton of part replacements and then something does not work right, you will have to back-track everything that you did....which could be very time consuming and fustrating to say the least.....
I just re-read your post....you work on synths so you should not have any problems modding this unit....if I find a schematic I'll let you know....
 
Thanks for the response. The seller says that the mixer works fine, but I assume there will at least be some noisy pots.

The power supply is something I read about in another thread. A user named Beck mentioned it. He did replace the opamps, so maybe that was why he had a problem with the power. He used OPA2604's, and the datasheet does say that they use a bit more current than the 4560's that come in the mixer.

I plan to replace all the caps. I am not sure about the resistors - lots of work. A schematic might help me locate only the ones that the sound actually passes through. I think that they would be the most important ones, and not pull-down resistors or dividers.

Whatever I do end up doing, I will do it one channel at a time. Then I can check for errors and do a/b comparisons between the channels.
 
Ok I have the mixer now. It seems to work pretty well. There are some noisy pots and some of the input jacks wiggle around too much. I will reflow the solder on all of the jacks.

The only thing I am having difficulty with is listening to channels 1/2 or the main mix with headphones. For some reason I can only hear 3/4 or PFL in the headphones. Any suggestions?
 
Ok I have the mixer now. It seems to work pretty well. There are some noisy pots and some of the input jacks wiggle around too much. I will reflow the solder on all of the jacks.

The only thing I am having difficulty with is listening to channels 1/2 or the main mix with headphones. For some reason I can only hear 3/4 or PFL in the headphones. Any suggestions?

Do you get any sound from channels one and 2 through headphones??......and you can't hear the main mix on headphones......but the main mix is at the mains output jacks.......

If you are getting sound from the main output jacks from channels 1 and 2 but not in the headphones, then there could be a connection problem.....is there a switch that routes channels 1 and 2 to the headphones??
If there are any routing switches there then you might try a shot of Deoxit......I would rule out the simple and easy stuff first before I tear too deep into it.....FWIW...I would get these issues fixed up first before upgrading with new parts....I haven't seen a schematic.....did you try to contact Tascam?? if you google them the company website will come up........contact info should be there......
Cheers
 
I don't see a button for 1/2. There is only one for 3/4. So I don't know if the headphones is only for previewing. But that doesn't really makes sense. That is why I was asking - I was hoping someone with the mixer could confirm.

The main output works fine though. It is just getting the 1/2 sub channels to the headphones. I think that it is the switch. They seem a little weird and stick sometimes. I haven't opened it up yet. I am going to do that today. I expect to have to do a lot of cleaning before I even look at the electronics.

I did find a manual and service manual (I think). I found a generic one for the M-200 series. It doesn't mention the M-224 specifically, but what it shows looks identical per channel. I think that will help me out a lot :)
 
I don't see a button for 1/2. There is only one for 3/4. So I don't know if the headphones is only for previewing. But that doesn't really makes sense. That is why I was asking - I was hoping someone with the mixer could confirm.

The main output works fine though. It is just getting the 1/2 sub channels to the headphones. I think that it is the switch. They seem a little weird and stick sometimes. I haven't opened it up yet. I am going to do that today. I expect to have to do a lot of cleaning before I even look at the electronics.

I did find a manual and service manual (I think). I found a generic one for the M-200 series. It doesn't mention the M-224 specifically, but what it shows looks identical per channel. I think that will help me out a lot :)

I took a look at some pics on google......but couldn't see much.....You were lucky to find a manual......if it is for that series of mixers, then the channel and routing sections should be the same......the power supplies might be different as in the particular ratings of components.....such as transformer, diodes, capacitors, and resistor wattages......but the basic design would still probably be the same......

I had originally thought you were referring to channels 1 and 2.......but it is the subgroups 1 and 2.....can you send me a link to the manual......

please note.......I am by no means an expert....I do repair most of the gear for the local music store....and for pretty much most of the musicians and schools in the area.......if I can be of any help I will be happy to do so.......many people in the past have helped me so it is only right that I try to do the same....


you mentioned switches for the sub-groups?? give then a few squirts of Deoxit.....that might be all that is wrong especially if this board has been in storage for some time.....you no doubt have noisy pots and faders....give it a very good cleaning first and then see where you sit....
Cheers
 
It's a nice mixer as it is stock. I still have the M-216 and M-208. If you want to mod the op-amps first thing to do is desolder the original op-amps and solder in high quality 8-pin machined DIP sockets. Machined sockets are far Superior to the standard. Once those are in you can try different op-amps. The early M-224 were a bit underpowered because they added 8 channels, but used the power supply circuit from the M-216. It's fine with the original JRC4560 op-amps, put the BB OPA2604 draw significantly more current, so when you fill a board with them the PS in the M-224 will struggle to keep up. The JRC4580 is the newest and best of the 45xx series and beats the socks off the 4560. You can try those, and of course the venerable NE5532, which is still one of my fav op-amps.

Pulling carbon film resistors in the signal path and replacing them with metal film types is one of the best things you can do to cut down on thermal background noise/hiss. You don't need to replace every resistor in the board; just those in the signal path
 
Thanks for the info Beck. I might give those mods a try in the future. Right now though, everything is working well enough to keep me happy.
 
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