TASCAM M3500....just picked one up!

  • Thread starter Thread starter altruistica
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altruistica said:
I also removed the three IC's which are in sockets and re-fitted them. When I turned the mixer back on, the noise was gone. I'm wondering whether I should replace all the caps in this section and the three IC's NJM4580.
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It's very rare for ICs to go bad. Bad electrolytic caps are much more common. In fact, that's the most common failure in old electronics. The ICs you reseated probably had dirty socket contacts that were cleaned by removing and reinserting them.
 
I dont know the workings very well of Tascam desks. But Ive run into problems with other desks that were in a smoking environment for years, Namely, if the console was wired in its previous location with cables plugged into the the sends and returns to go to say a patch bay...then you try to use it without all those plugged in and you get dead channels. I found its due to smoke and tar buildng up on the contacts of the send and return jacks, so when no plugs are in them they arent making a good a"through" or normaled connection. When I converted to my last console (a DDA QII) this was the major issue with it after removing it from the studio and re=commishing it at my place. Deoxit an dQ-tips re your friend....
 
mdainsd said:
I found its due to smoke and tar buildng up on the contacts of the send and return jacks, so when no plugs are in them they arent making a good a"through" or normaled connection.
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Excellent info. We don't usually consider the effects that unused jacks may have on the signal path.
 
Hi Guys,

Thanks for all the tips so far.

I have found more than a few dirty insert points and jack line inputs. Also the odd pot or fader that hasn't been moved in a while that has come 'unstuck' and started working again.

But the first impression of the desk?

WOW! I like it.

It has a 'silkiness' about it, but with a cosy warm feeling too.

It definitely sounds 'fuller' than the Ghost I had been using and what is apparent is a sense of detail. If I find a part needs a little lift, then raising the fader very slightly just makes the part leap out, whilst not burying other parts. And that's just with the Fostex D2424LV as the sound source. I can't wait until the G24S come back from being refurbed and setup. I've got enough to do here though with re-siting the mixer. I'm thinking also of moving the piano (Yamaha U3) into the control room to make level setting up easier when I'm working on my own.

One question for the moment.

I take it that the mixer should operate Solo in Place when the PFL button is in its raised position? The PFL solo function works but when a channel is soloed using the SIP, nothing comes out of the mixer (I have checked the SIP pot is turned up). I presume the signal should come out of the CR (control room) outputs? I'm wondering whether a cable has been disconnected or become disconnected because the whole function doesn't work. Any ideas on how I should track down the following.

1) Low output out of all L outputs (STEREO, Control Room 'A' & 'B', STUDIO)

2) Headphone L not working

3) Pre-amps distorted on several mic pres

4) Occasional bursts of noise (think low frequency pink noise) on outputs, followed by it disappearing again.

I checked the Power Supply voltages and found:

+48V = 48.7V
+8V = 7.98V
+12V = 11.96V
-15V = -14.98V
+15V = 14.96V

All the measurements were with the console disconnected.

Cheers
Al
 
altruistica said:
I was a little apprehensive about unplugging too many cables inside the M3500, so I still have to fix the broken pre-amps. I need to probably fully immerse myself in the manual so I fully understand the single path.
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Have checked out the PS?
I mean...I would rule out any issues there first...that way, when you start checking voltages and levels, you know that ther PS is providing what is needed/expected.

<EDIT> OK, looks like you checked the PS.

The PFL...mmmm...god, I never use that, I just use solo.
I wsould have to check my manual to confirm if you are using it as design intends...but then, you have the manual too so I'm sure you will sort it out.

You do have a few CR options and monitoring options...so make sure you have all the right buttons engaged.


diggy_dude said:
...you want the test signal levels from all tracks to be the same when you play back the recorded test tone. It was a problem for me because some channels appeared to be dead or have greatly diminished levels. It turned out that the group cards were the culprit, not the channel cards.
Click to expand...

Yeah...if you had odd levels with the GP outs...I can see how that would be a problem.

Before I got all my outboard pres...I use to track through the 3500...but that was way back in the day, when the console was still relatively new, and worked to spec.
I'm actually quite happy that it's held up for 25 years without any major issues...but I can hear the "age" more and more.
Pots/faders getting too scratchy, too stiff, too soon after cleaning, pan pots losing their center "click" detent, EQs "chirping" when pushed too far on the + side...etc. Nothing that stops the show, but obviously things not top perfect spec and just getting old.
For my personal use, I can work around all that easy enough and not have any negative impact on the music...but if I needed to run in a more commercial environment, I would want all that resolved. which I'm sure would start with a full recap and overhaul.
 
The power supply should be tested under load, i.e. connected and console on.

Do you have a scope? This is the fastest tool for me to trouble shoot gear with.

Checking for ripple on the P/S leads will tell you whether or not you need to look at the big caps in the P/S.

Do you have a manual? If not, get one. Look at the block diagram (or flow diagram) and see where the the common point is for things on the L side. Then go to the schematics and get down to signal tracing with the scope. I assume that desk has a built in oscillator, use it and probe away.

Intermittent noise often comes from dirty or oxidized edge or ribbon connectors.

Distorted channels. Could be lots of things, but electrolytic coupling capacitors degrading is a place to look.

Also, swap channel strips, see if the problem follows the strip or if it stays in place.
 
Hi Guys,

So I'm getting a bit deeper into the issues with the mixer. I think the problem with meter 27 lies within the meterbridge itself, as I've exchanged a 4-input module over and it stays the same....it could be a problem with the lead going to the meterbridge. Is this the top most three pin lead? I'll look it up on the schematics but I thought I'd ask just in case someone has been here before. As far as looking into issues with the input cards, it looks like the cards are divided into two sections, with a connecting 4-piece board connecting upper and lower halves. Is this so you don't have to remove all the nuts in order to get at a channel? What's the best way of removing the 'JOINT PCB' board and the 'SUB BUSS PCB' board? My instinct was to slowly try to pry them apart working from each end?
 
It's been awhile since I opened up my 3500 to expose its guts.
Those boards...yeah, I think you just have to "work 'em" gently, and they should come apart...and it should be obvious which are meant to come apart.

AFA the meter...it's been ages since had that open. I would have to refer to the schematics, which you can obviously also do for yourself.

I've not had to do a lot of repairs on my 3500...which I'm not sure if it's been luck or just the fact that I've not ever abused it. I mean...I've seen other guys who picked up used 3500 consoles and who had similar issues all over the board, but then I know of others who had few issues. I also think environment has a lot to do with it...mine has always been in a proper, climate controlled studio...not a lot of dust, or a lot of smoking (a bit of tobacco in the early few years, but not for te last 20 years. Plus, my power has always been conditioned and voltage regulated.
There are days when I go to power it up, and I'm almost waiting for it to go "FIZZ"...:D....just for the fact that it's over 25 years old, and it hasn't had any real issues. (I hope I didn't just jinx myslef ;) ).

Most of my work on the 3500 has been cleaning of pots/faders/connectors...I modified the balanced XLRs to + Pin 2 instead of + Pin 3...and maybe a couple of minor internal connectivity/signal issues that were solved easy enough.
 
Thanks Miro,

Actually after getting some of the boards out, they do look surprisingly good for their age. After looking at the 'joint boards again, it looks like it might be easier to remove them once all four boards are removed from the panel. The upper boards then look like they could be slowly prised away from the joint board, as opposed to prising the joint board away from the input boards. I'll keep y'all informed of how I do.

Al
 
altruistica said:
One question for the moment.

I take it that the mixer should operate Solo in Place when the PFL button is in its raised position? The PFL solo function works but when a channel is soloed using the SIP, nothing comes out of the mixer (I have checked the SIP pot is turned up). I presume the signal should come out of the CR (control room) outputs? I'm wondering whether a cable has been disconnected or become disconnected because the whole function doesn't work.
Cheers
Al
Click to expand...

Both the PFL or Solo (depending on which is selected) should come out of the monitors when pushed down. Remember they are on separate volume controls. I use both quite a lot.

Alan.

P.S: I also meant to add to the above suggestions that before anything else, pull the console apart and disconnect / reconnect all the ribbon cables, if the console has been out of use for any amount of time there could be some corrosion on the contacts and this could be 90% of the problem.

The other thing I have happen is that the insert plugs are not making internal contact when nothing has been plugged in, this makes the channel dead. A easy test is to make a stereo jack with the tip and ring shorted, when this is plugged in the insert is bypassed and it will prove if there is a bad internal contact.
 
Hi Guys,

Thanks for all those tips.

I've currently bit the bullet and disconnected everything. It's allowed me to remove the four module input panels, remove the channel boards and give the panels a good clean. It took a day to remove all the boards and screw them back together. I'm going to get the Hammerite paint out again (remember the Fostex D2424LV MKII I had a problem with.....well I did eventually strip that unit down and re-paint the carcass and now it's as good as new......well better caus' the galvanised paint isn't going to rust). Parts of the console chassis are suffering from the same thing. A little rub down and a tickle of paint should stop the corrosion. Does anybody test caps like this BTW:

https://www.youtube.com/watch?v=J9-k0HgGzbU

I've seen this kind of test before, never tried it though.

Thanks Alan for the confirmation on the SOLO function. There's definitely something wrong with the Solo In Place function as there is nothing when this is selected and a channel is soloed.I take it the channels that are unselected from SIP, their MUTE lights don't illuminate? On a Soundcraft GHOST when SIP is used, the other channels' MUTE lights come on to indicate SIP as opposed to PFL. I hadn't seen that on a console before.

Al
 
Interesting method of checking caps. Never saw that. It said though it wouldnt work for a shorted cap, but seems to catch the leaky ones.
 
Going to be in for a long haul methinks........

I had a look at the meterbridge last night to see if I cold sort out the LEDS which stay on channel 27. After reading about level setting and tweaking the pots, I left turning it on until this morning. When I turned it on, hey presto, the meter was no longer stayed illuminated. I did a rough mix of a track as after thoroughly cleaning the mixer, I'd decided that I would use it for a while nd see what else needed fixing.

Well I only turned it off once to find out possibly quite a bit needed fixing. After turning it back on, it did its crackle and splutter, only this time the meters were going a bit mad too.

I decided that I should check the Power Supply under load as previously suggested. This required removing from the rack and getting it behind the mixer with the top off of it. Sure enough, the +8V rail had disappeared down to 0.71V....I thought at first I had the meter set wrong, but no it was dead. So I bit the bullet and dismantled the PS to find some strange readings in the caps. I've recently bought a great multimeter (a Bryson 765 I think it is). It can check caps so after finding quite a few off spec (some as much as 40% off) I decided to oreder some parts and to re-cap it all. IAfter checking some off the input boards, I think I'm going to have to re-cap some of them, along with much of the MASTER section, but I thought I'd start with the PS as without a stable supply, the mixer could be doing anything.

Keep you posted.


Al
 
altruistica said:
... but I thought I'd start with the PS as without a stable supply, the mixer could be doing anything.
Click to expand...

:thumbs up:

That's what I was saying earlier.
You would just be chasing your tail on all the other issues...with a faulty PS.
 
Yeh, you're right Miro.:thumbs up:

Before the mixer went AWOL though, I have to say, I think I'm going to like this mixer. One track I was working with pointed out something I'd never heard before. On the stereo submix of the drum track, it seems I when I submixed it, I hit the occasional level a little too high and had the odd red indicator of the Fostex D2424LV illuminate. Although these are momentary peaks (lasting probably less than 0.5secs), I'd never heard any distortion before, but with the Tascam, it was clear as day, especially as it was only illuminated on the R hand side of the submix. It seems to give a very clear, open sound without any muddiness or tubbiness. If it sounds like this with knackered caps, I can only imagine (hope!) that it's gonna sound brilliant once it's sorted out.

Al
 
+1 to the power supply work. That 8V rail powers your switching logic. Underpowered ICs do really weird stuff. Just get it recapped, recheck voltages under load, and scope the rails to make sure they're "clean" (no AC components in the DC rails). These tests will ID failed rectifier, bad regulator, etc. I bet some or even most of your problems are abated with the PS getting some attention.
 
HI Guys,

I did the Power Supply and was getting ok voltages until I connected the desk. Once again the +8V rail disappeared, so I started to disconnect some of the rail ribbon connectors (with the power off of course). The mixer was stable until I added the 'MASTER' section into it. After disconnecting the MASTER section (8 boards that house the group outs and all the other outs along with normal master functions) I found more than a fair share of caps well below spec. I'm awaiting on replacement caps, but once I've done this, I'm then going to check all ICs are fitted correctly, then connect the main rail back (three separate ribbon connectors) without any of the OUT connectors connected and see if the Power Supply is stable. If it is, I'll add the OUT connectors back to the boards (maybe one at a time if there are problems) and try to isolate which board might be causing the problem.

Stay tuned.

Al
 
I know you checked the PSU rail voltages, but that is in most cases, not much of a worthwhile test. Like has been said, the real test is what the PSU does under load. Yours is tits up at least with the logic rail. Really, it's best to use a dummy load as opposed to the device to test the power supply. Maybe it is something in the mixer frame...maybe not. By loading the PSU with a dummy load you take the mixer out of the equation and isolate the PSU. Always start with the PSU when there's trouble.
 
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