MS-16 story

  • Thread starter Thread starter evm1024
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I can answer that

sweetbeats said:
So, Pete, just for my own education, what has led you to seek a replacement for C42 (i.e. how do you know it needs to be replaced, or otherwise upgraded)?
Click to expand...


C42 is the coupling cap that feeds the bias signal into the bias level pot and thus on to the sync head. Increasing the value of C42 to around 200 pF (in this case 180 pF) is the mod to allow these channel cards to bias a +9 tape correctly.


--Ethan
 
Movinng forward

I'm moving forward with this deck. Many thanks to Talldog (Ken) for sending me the arming panel, and a bunch of other needed parts.

I took a quick function test and found that the machine does not select input/sync/repro as it should. Given that some of the CMOS logic had holes blown in them it appears that the problem is up-stream. I'm a bit pinched for time but I'll see what I can do over the next few weeks.

All channels except ch1 can pass an input signal at least to the meters.

I don't have an extender card so perhaps I'll have to make one up. That should speed things up a little. Getting this going to the point I want it to be may be a bit of a saga. But, I'm having fun.

Here is a photo of where it is now.....looking pretty!

--Ethan
 

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Ethan, congratulations on what you've accomplished so far...it does look great.

Wow...I'd be so dashed if I was running into your problems...wouldn't know what to do. It is a real encouragement that you calmly take even the complicated technical issues in stride. That deck will be back into full service for sure.

Thanks for the great thread!

Hey, if the 58 and MS-16 amp cards are the same, then I'd assume the extender card is the same as well. I have one if you want to borrow it. I imagine I won't need it for awhile once I can get the bias circuitry dialed in...Not sure how we would work it out logistically but I need to borrow your o'scope to check my bias circuitry and when I'm done with the o'scope I'm done with the extender card for awhile too.

PM me if this sounds like a good (foggy at this point) plan.

Does your manual list the p/n for the extender card? My 58 manual does in the section on the bias adjustments. It is p/n 5200096100. Should be the same, but just in case, see if you can find the p/n in your MS-16 manual...
 
Hey thanks so much for checking out that part for me ethan. This is a great thread. I'll be sure to keep you posted on this mod. I plan on using ATR tape on the machine.
 
The same

sweetbeats said:
Ethan, congratulations on what you've accomplished so far...it does look great.

Wow...I'd be so dashed if I was running into your problems...wouldn't know what to do. It is a real encouragement that you calmly take even the complicated technical issues in stride. That deck will be back into full service for sure.

Thanks for the great thread!

Hey, if the 58 and MS-16 amp cards are the same, then I'd assume the extender card is the same as well. I have one if you want to borrow it. I imagine I won't need it for awhile once I can get the bias circuitry dialed in...Not sure how we would work it out logistically but I need to borrow your o'scope to check my bias circuitry and when I'm done with the o'scope I'm done with the extender card for awhile too.

PM me if this sounds like a good (foggy at this point) plan.

Does your manual list the p/n for the extender card? My 58 manual does in the section on the bias adjustments. It is p/n 5200096100. Should be the same, but just in case, see if you can find the p/n in your MS-16 manual...
Click to expand...

It is the same extender card (listed in the ms-16 manual and 58 manual)

The scope is available whenever you want it. I can give a 5 minute tour of operation if you need to come up to speed with scopes.

Let me know and I'll bring it in to work here in Beaverton. and we can go from there.
 
ood news and bad news...of course

Well, I recorded my first thing on the MS-16 tonight. Thats the good news. The bad news is that I needed to use the spare channel card that Talldog sent me because every channel card that came with the deck needs fixing. Thats the bad news.

It could be that whatever blew up the IC took out the other one as well. They are both 4000 series CMOS and run off the +15 volt supply... Max for CMOS is +18. Everything else should be able to handle some higher voltages.

I just dug around and found the 2 chips that I needed. After replacing both the channel card functions properly. Well, that is an "easy" fix. I think that I'll use sockets on these devices.

--Ethan
 
One more teaser

I'll toss a teaser into the mix.

I've been looking through the schematic and see where you can change the speed. the manual hints at speed changes. Now for the kicker. It appears that you can run it at 30 ips as well as 7.5 ips :eek:

Lastly, the schematic shows an elapsed time device. Next time I've got the back panel off I go look for it. It would show you the total hours on your machine!

Once I get the channel cards fixed I'll have a go at 30 ips. Expect photos!

--Ethan
 
That deck was meant for you, Ethan...I can't think of anybody that would try to resurrect it rather than use it as a parts deck...wow. That's not a criticism on what you are doing. I think its is nothing less than fantastic.

Funny thing...I did my first recording (other than test tones) on my 58 tonight. :D

So where are do the speed control and elapsed time thingies reside? Wondering if there is anything like that on my 58...the control PCB? Really, really interesting.
 
Installing sockets for the chips is a good idea.... won't require any extra soldering and will sure make life simpelr if you blow another chip!







AK
 
Sockets, speed and chips....

Talldog, Yes one of the 2 cmos chips was socketed. This is what allowed me to test. (I scavenged the device from your channel card).

Analogkid, They blew up once.... I presume that the PS went south and or something else messed up the +15 supply for a while. Hopefully not again for a long while....

Sweetbeats, Looked over the 58 manual. The 58 uses a different speed control mechanism than the MS-16. Changing speeds to 30 ips is built into the MS-16 but not to the 58. The MS-16 uses a PLL (phase locked loop) to control speed whereas the 58 uses an analog comparator. Both use the "same" 9.6 MHz osc for their speed reference. The Pll divides this clock down to end up with a 600 Hz signal to phase lock to (differences in phase produce a correction voltage). Because it uses a divider you can easly produce a 1200 Hz reference for 30 ips or 300 Hz for 7.5 ips. In the 58 the capstan tach goes through a freq to voltage conversion which gets compared tot he reference voltage (which is derived from the 9.6 MHz reference clock).

I'm sure you could change the speed but that would be work! (all this from just a quick look so take it with a grain of salt)

The 58 audio is the same as the MS-16 so they should be the same acoustically. Same channel card, same -10 dBv to +4 balanced circuits. Many of the same controls.

Regards, Ethan
 
Ethan, thanks for taking a peek. I'm good enough to leave well enough alone as far as the tape speed on the 58. :)

Hey Talldog, got my care package from you yesterday. Thank you so much...can't thank you enough...got the channel cards, the "angle thingies", the PCB layout and parts sheets and the CD! :D:D:D Haven't had a chance to check it out yet, but I certainly will! Guys, if you're bored and feel like boosting somebody's rep, dish it out to Talldog...even if you're not bored for that matter...and to Ethan too for this awesome thread...shoot...REP FOR EVERYBODY!!! :D:D:D
 
*****
Five stars for the thread, ... even though I personally have no use for it :( :( :(
maybe someday.

Good going, Ethan! :)
 
Relay replacement

It has been crazy at work and at home but I did get around to ordering the replacement CMOS logic and relays for the channel cards. I thought that as long as I was doing them I would do the relays too.

The original RD22v-1S (NEC) relays are not to be found. Lots of others that will fit. I decided to give the Omron G5v-2-H1-DC24 a try. These are the extra sensitive relays that only take about 8 mA which is good as that it presents a lower load to the driving transistors. It will have to wait on getting the originals off the boards to see if this was overkill. Coil resistance is the thing that can be measured. Standard relays take about 25 mA to activate with the next most senisitive needing about 15 mA.

These relays are common for the channel cards of the MS16 and Tascam 58 among others. Let's hope they drop in.

DigiKey part number Z110-ND at about $3.18 each.

Now to find the time....
 
Best of luck with the relay replacement Ethan. A replay was bad on one of my 58-OB's cards and I was too intimidated by the prospect of replacing it so i just got a new card.

A little update on my MS-16:

I replaced the bias feeder caps with the 180pf poly film ones for all the channel cards. Worked great.
I set up the machine for +9 operation with an MRL tape.
I did the record alignment using some gp9 tape. Compared to the MRL tape the bass bump was enormous (about 6db at 50hz) but after adjusting the low freq pot I got the response to something like +2.5db@50hz 0db@100hz 0db@1khz -0.5@10khz
The I think azimuth is pretty messed up though. I'm going to need to call a tech in to adjust that. I'm still awaiting the new pinch roller from Terry Witt. But i wonder if the hardened,shiny roller is what's causing waver at 15khz or maladjusted azimuth?
 
ethyrvalve said:
The I think azimuth is pretty messed up though. I'm going to need to call a tech in to adjust that. I'm still awaiting the new pinch roller from Terry Witt. But i wonder if the hardened,shiny roller is what's causing waver at 15khz or maladjusted azimuth?
Click to expand...

Head alignment should be done before any other adjustments. Do you not have an o'scope to look at the azimuth or are you lacking the proper tool to adjust the heads?
 
No I don't have a scope, I was just trying for a ballpark adjustment to see if it works ok. at this point I don't really feel confident monkeying with the heads.
Would you say it's fairly easy to learn how to do?
There's a great tape tech in my neighbourhood who i'll call.
I just tried checking the azimuth by patching channels 1 and 16 then 2 and 15 to my mixer and flipping the phase. the cancellation of 40hz and 1khz tones was pretty much total. for 10khz... not so much.
When i first got the machine i needed to reattach the tension rollers and i boneheadedly managed to lose one of the set screws so perhaps the azimuth of the roller itself is slightly off.
 
The basics of checking head alignment are pretty simple. The service manual for the MS16 should have the exact procedure for you to follow. I've never attempted the method you described but from your description, it appears that your azimuth is way off.
 
Pete,

Checking the azimuth the way you are doing it is one way to do it without an o'scope, or you can set track 2 for -6VU (on an external meter), and track 15 for -6VU, sum them and they should be 0VU. Similar to flipping the phase and looking for total cancelation...this is what I used to do, but I'm now using a PC-based o'scope that works fine for this type of work. It is Blue Cat's Oscilloscope Multi. Its a .vst plug, but there is also a directx version. Shareware. Demo version is unlimited use but limited functions, but enough for doing azimuth.

I was a little intimidated with azimuth work, but it is actually pretty simple once you have the right tools, and since the heads are mounted fast to the headblock on the MS-16 you just make sure the head-mounting screw is tight, and then adjust the azimuth adjustment set screws one way or the other to get the right position as shown on the scope and then tighten the other to fix the position. A little tweaking will be required once you tighten the second screw, but it is pretty straight-forward. Maybe have your tech friend come over and walk you through it? Or I could even put up a little video if needed. Let me know.

Ethan and Pete, thanks for posting the detail on the mods you are doing. It will be very helpful later on! ;)
 
Hey thanks for the head's up on that plugin Cory. I'll download it tonight. I now have a PC in my basement so I can use it. (After years of being a Macintosh partisan i've come to realize that I despise all computer manufacturing corporations equally:)).
 
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