Login / Register
 
Eventide Harmonizer Model H949 Questions
New Reply
Subscribe
apprenticemart2
Thread Starter
#1
16th February 2012
Old 16th February 2012
  #1
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
Eventide Harmonizer Model H949 Questions

Hi Everyone, I have some questions about my non working H949.

Are the green caps tantalums? They are 0.33uf,can I use 0.1uF instead?

I have other tantalums, they are 6.8uF and 16v. Can I use 0.1uF instead?
This one looks like it's the wrong way around(Top),is it a mistake on the board(HD921 Rev C), or does it not matter for this location?

Does anyone have the schematics, resistor/capacitor chart and any calibration tips, for this revision of DBX board?


While I am here, I would like to ask about the long black ones(Caps?). I have seen them before in Apple II computers. What is the story behind these, and what can I use instead if I find one that has been blown?

Any information I can use to help wake me up from this nightmare, will be greatly appreciated.
Thanks
Martin
#2
17th February 2012
Old 17th February 2012
  #2
Gear maniac
 
WTMNMF's Avatar
 
Joined: Oct 2005
Posts: 277

WTMNMF is offline
>Are the green caps tantalums?
No, ceramic.

>They are 0.33uf,can I use 1uF instead?
Maybe, but why?

>I have other tantalums, they are 6.8uF and 16v. Can I use 1uF instead?
Again, why?

>This one looks like it's the wrong way around(Top),is it a mistake on the board(HD921 Rev C), or does it not matter for this location?

Might not, but in general tant's want to be oriented carefully, as they tend to catch on fire and burn holes through the PCB when backwards or failing to a short. Does it appear to be old solder? If it's been their and not blown up, then it must be in a circuit that is not polarity sensitive ( although it is bad practice to put the polarity designation on the PCB, in that case ). Eventide PCB's are loaded with errors, so it could be that the designation was wrong and it's noted on the schematic and/or in an ECO ( engineering change order ). I don't think that they ever thought a board was flawed enough not to use

>Does anyone have the schematics, resistor/capacitor chart and any calibration tips, for this revision of DBX board?
Eventide sell a service manual for about $35.

>While I am here, I would like to ask about the long black ones(Caps?). I have seen them before in Apple II computers. What is the story behind these, and what can I use instead if I find one that has been blown?
Axial lead tant's.

When replacing cap's:
Higher voltage rating is always OK, as long as you can fit it. For supply related cap's, capacitance in the same order of magnitude is going to be fine.
For filter and timing circuits, they need to be close to exact, unless you understand the circuit well enough to determine otherwise. Obviously, you can replace a 40% part with a 20% part of a different value, and still be within the design tolerance. As a matter of fact, the use of a low tolerance part should give you a big clue about how critical the capacitor value is in the circuit. When you see a wide tolerance, you should hear the engineer's voice saying 'about xx uf here'.
The capacitor type may be changed in many cases, but again, you will need to understand the circuit's function to determine that. As long as the ratings are correct, you won't hurt anything by experimenting, but it may not work properly, and/or sound bad/different.


The real question is, why are you worrying over all of these cap's?
Start with the basics. Break the thing up into functional blocks and check them, starting with the power supply. Of course, it never hurts to look over the thing for obvious failed components or mechanical faults. 99.9% of all electronic devices that have survived their first 24 hours of life, will fail due to something that started with a mechanical fault. With an old device like this, you can just go ahead and replace the electrolytics in the power supply, as they may need replacing at some point anyway. On the other hand, it doesn't make much sense to bother if you're not confident of completing the repair.
apprenticemart2
Thread Starter
#3
17th February 2012
Old 17th February 2012
  #3
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
Thanks for the reply.

>Are the green caps tantalums?
No, ceramic.

They have a polarity marked on them, and so does the pcb?

>They are 0.33uf,can I use 0.1uF instead?
Maybe, but why?

I thought 0.1uF/100nF was the holy grail of decoupling caps,plus I have a few, and although the schematics aren't very clear I see a lot of 0.1uF going to ground.I'm guessing they may have specced 1uF but used smaller values as a cost saver?

>Does anyone have the schematics, resistor/capacitor chart and any calibration tips, for this revision of DBX board?
Eventide sell a service manual for about $35.

From what I can gather from archived posts on other forums and here, there were 5 revisions of the DBX boards. Maybe Eventide have schematics, but I doubt they have component selection charts for DBX boards. I will try them however, as you may be correct. The schematics I have for the DBX board is not compatible with my version.

I have stripped this down to the bare bones, and am considering replacing most of the capacitors. I have already done the Electrolytics in the PS as I had some lying around. As I can only test Capacitors out of circuit (I am not knowledgeable enough yet to test caps in a live circuit with an oscilloscope) I may as well replace them. I have already found some dead tants on the DBX boards.

Thanks for your help
Martin
#4
17th February 2012
Old 17th February 2012
  #4
Lives for gear
 
Radardoug's Avatar
 
Joined: Oct 2009
Location: Northland New Zealand
Posts: 554

Radardoug is offline
Going through and replacing all the caps is not likely to be the problem. Eventides of this vintage used mixed logic families and are usually full of logic faults. The only way to fix them is slowly! The unit is likely to have multiple faults. However there are certain givens with Eventides.
Recap the power supply and make sure you have good rail voltages.
The Molex connectors used for the power connections will be faulty. Replace them, if possible with a better type of connector.
Then just work your way through the circuit.
apprenticemart2
Thread Starter
#5
17th February 2012
Old 17th February 2012
  #5
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
That's good advice. Some of those molex connectors are a little burnt looking.

Thanks
Martin
apprenticemart2
Thread Starter
#6
27th February 2012
Old 27th February 2012
  #6
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
Can I use an LM339 instead of a MM74C909?

Can I use an LM339 instead of a MM74C909?

They are cheaper which is why I would want to use the LM339
#7
28th February 2012
Old 28th February 2012
  #7
Lives for gear
 
Radardoug's Avatar
 
Joined: Oct 2009
Location: Northland New Zealand
Posts: 554

Radardoug is offline
On a quick look the pinout looks similar, so the answer is probably. But I've never had one of those fail in a 949.
#8
28th February 2012
Old 28th February 2012
  #8
Lives for gear
 
Joined: Jun 2008
Location: secluded tranquil country
Posts: 2,974

The Real MC is offline
Pinout may be similar but the risk is input loading and fanout. The 4xxx CMOS family doesn't have a hefty output stage. If the inputs of the '339 loads down the output(s) of CMOS upstream then you risk slewing of the signal or drooping. The '339 may not operate at power rails like the CMOS can. If the '339 swings too fast the overshoot may really throw a monkey wrench at the whole thing.

Eventide may have had an engineering reason to use the CMOS part. In something as insanely complex as the Harmonizer, I'd put my money on an exact replacement.
apprenticemart2
Thread Starter
#9
29th February 2012
Old 29th February 2012
  #9
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
Thanks
#10
1st March 2012
Old 1st March 2012
  #10
Gear addict
 
SP2016's Avatar
 
Joined: Jan 2010
Location: the Netherlands
Posts: 478

SP2016 is offline
Quote:
Originally Posted by The Real MC View Post
Eventide may have had an engineering reason to use the CMOS part. In something as insanely complex as the Harmonizer, I'd put my money on an exact replacement.
The reason might be that there are a lot more CMOS parts in the H949 and that CMOS was quite common and easily available in the time that the H949 was designed.
Eventide just used parts typical for that time.

To play it safe: Use the same part (if you can get one...)
And replace the blue tantalium capacitors on the dBx boards, especially the two thick ones.
apprenticemart2
Thread Starter
#11
23rd June 2012
Old 23rd June 2012
  #11
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
I finally got this working in case anyone is interested.
I found 4 ceramic caps on the top digital board that had become resistors so I replaced all decoupling caps in the whole unit so there wouldn't be any more chances of a problem.
I replaced all caps and regulators in the power supply. A couple of ribbon cables needed replacing and a 74C901 was needed for the function LED's. I also replaced all the op amps on the analogue board.

There was 1 blown tantalum on the expander board, and the associated op amp had also blown. I replaced all the tantalums in the whole system, especially the DBX cards.

All vias were re-soldered and various untidiness due to bypassed power connectors using jumper wires (bad caps drawing too much current overloading connectors?) was, well tidied up. I also changed a TL081 on the digital board next to one of the DACS as it didn't seem to be behaving properly. WOW, I think that's it.

In conclusion, I'm surprised at how quiet it is. I had heard that these were supposed to be noisy?
One final thing. I should be able tu run 4 x 29C01's in this instead of 2901's, and would like to because they run a lot cooler, and I could then put this in a rack without it frying the rest of my gear. But they don't work. I can install 2 x 29C01's and then after that I get a lot of noise if I put in 3. Timing discrepancies? H949 with Rev C digital board.

I had to put the egg frying chips back in, but I think they sound better? The splices seem better on algorithm 1.

Cheers
Martin

Last edited by apprenticemart2; 23rd June 2012 at 10:34 PM.. Reason: new info
#12
24th June 2012
Old 24th June 2012
  #12
Lives for gear
 
Radardoug's Avatar
 
Joined: Oct 2009
Location: Northland New Zealand
Posts: 554

Radardoug is offline
Well done that man! Re the 2901's, yes there is probably some slight timing discrepancy causing the cmos ones not to work. I wouldn't worry about it apart from the heat factor, maybe you could put a little fan in there? That would be good for all of it.
apprenticemart2
Thread Starter
#13
24th June 2012
Old 24th June 2012
  #13
Lives for gear
 
apprenticemart2's Avatar
 
Joined: Feb 2012
Location: Old Oswestry
Posts: 579

Thread Starter
apprenticemart2 is offline
I was wondering about reading the proms off and programming some MB7112L as they run a lot cooler, but I don't think I'll bother now as they may not time the same as the DM74S288's, and also they are a pain to program as they need 20 volts to melt an aluminium fuse rather then the more common 10.5volt programming.

Cheers
Martin
#14
28th December 2012
Old 28th December 2012
  #14
Gear interested
 
Joined: Jun 2012
Posts: 27

thendara69 is offline
hi just wondered if you got it working?
New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
cl516 / High end
4
MatthewleBlom / High end
9
dingo / So much gear, so little time!
10
Clueless / So much gear, so little time!
42
tuRnitUpsuM / Music Computers
0

Forum Jump

SEO by vBSEO ©2011, Crawlability, Inc.