Dolby 363 mods - let's make a definitive list

[dcollins]

Originally Posted by Mark Williams

H, Group -

I've searched and haven't found a topic that directly addresses modifying the 363 for improved sonics (although many mentioned doing that in passing), so I would like to open that up.

Specifically, I am a mixer and some of my work is printed to an MCI JH-110b 1/4" machine. I use 1/4" and 15 ips/IEC for the tape sonics but want SR to control the noise. Quite apart from the advisability of using noise reduction at all, the 363 could sound better and mods have been around for years. My problem is that I have a 363 that I would like to have modified but I can't seem to find any notes on exactly what part and circuitry changes to have made.

I just wire it unbalanced directly to the card. There is no other mod that I would attempt.


DC

[Mark Williams]

Thanks and I think I may have seen your unbalanced mention in another thread. Not a bad idea but the rest of my rig is balanced and I want to maintain that as much as possible. I think there are subs for the IC's (dif amps, etc.) and that is what I'm trying to learn about.

Regards,

Mark

[The Orbit Room]

I'd start with the basics. Check and if needed stiffen and better regulate the PSU. Pop the top clear all dust bunnies, check rotation and any worn bearing or just plain noise from the fan. Check to see if the frame enclosure is straight and true. Clean and possibly VERY lightly lube the guides that the left and right edges of the NR card PCB travels on. Make sure the NR card edge finger traces as well as the mating card edge connectors are tarnish, dirt, dust, and gummy residue free. Make sure the NR card seats squarly,snuggly and secure in it's connector. The I/O XLRs get a little tarnished and worn after a while. Consider replacing them with newer Gold Pin connectors if possible.

Once the mechcanical, PSU and connector check/work is done, you may wish to have a general overview look at the components mounted on the PCBs. Most 363 units have been in service for years and with no Power Off switch have been sitting quietly cooking the parts of the rather well populated CAT 300 board(s). Look for swollen or bust electrolytic caps, burn or char marks on the resistors or PCB. Since the 363 is a stereo unit place the cards open side by each and look for any telltale differences between them. It may be advisable to replace the electrolytics with fresh new parts, and with a higher operating tempurature rating than original when possible.

I'm not going to step into the "which cap is best" beartrap. There are others on the forum who have done component level work on these cards and I will defer to them.

Best of Luck with it all.

Cheers!

[Mark Williams]

Very good -

I appreciate it.

Anyone have thoughts on subs for any of the chips? Here's a link to the manual (including a circuit print I believe), thanks.

<http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/151_363_8.Manual.pdf>

Regards,

Mark

[The Orbit Room]

I reviewed my 363 manual and on first blush it seems that the MB Ckts are really loaded for bear in regard to RFI suppression. Several small value caps in the signal path and design. Very much like the I/O of an DBX NR lunchbox rack card design.

I don't want to say the 363 MB is over designed, but it is built to withstand a nuclear strike or the possibility of normal day to day operation .

I don't know if it is even physicaly possible but my first thoughts turn to input iron. I'd have to have another look at the schemo, but I'm thinking a 4:1 xformer on the front end(s) up into the input trim amps.

Midnite thoughts,,,"night all.

[acorneau]

The only mod I can think of would be to replace the tiny adjustment pots with something you could use with your fingers instead of a screwdriver.

[Mark Williams]

input transformers and trim pots usable by human fingers are both good ideas!

Thanks,

Mark

[mrlouie]

since you are a mixer and not a mastering engineer here's something to think about..

lets say you do open up the 363 and do internal mods to it and get this really cool unit that you love how it sounds. since sr is an encode/decode thing are you going to send your modified 363 unit with the tapes every time you need mastering so that exact sound will be reproduced.

if you do mod your 363 i would also get a stock unit and play the tapes back off that after recording to see how it sounds, more then likely a mastering studio will not have a 363 modified just like yours once you go inside and start changing things around.

louie

[Mark Williams]

Originally Posted by mrlouie

since you are a mixer and not a mastering engineer here's something to think about..

lets say you do open up the 363 and do internal mods to it and get this really cool unit that you love how it sounds. since sr is an encode/decode thing are you going to send your modified 363 unit with the tapes every time you need mastering so that exact sound will be reproduced.

if you do mod your 363 i would also get a stock unit and play the tapes back off that after recording to see how it sounds, more then likely a mastering studio will not have a 363 modified just like yours once you go inside and start changing things around.

louie

Really good point! However, I use the 2-tr machine to print a mix and then immediately copy it back into the project. I deliver a digital master that is a copy of the analog playback. My setup methods are standard but I realize that altering the unit could influence decoding on another system.

thanks for that,

Mark

[dcollins]

Originally Posted by Mark Williams

Really good point! However, I use the 2-tr machine to print a mix and then immediately copy it back into the project. I deliver a digital master that is a copy of the analog playback. My setup methods are standard but I realize that altering the unit could influence decoding on another system.

Modifying or even eliminating the I/O electronics will not change the Dolby calibration or make your unit incompatible. The level metering is internal to the card, and all it cares about is that it sees a particular level.

In fact, even changing the opamps inside the cards (which I wouldn't recommend) probably wouldn't cause a problem either.


DC

[JustDucky]

Originally Posted by The Orbit Room

I'd start with the basics. Check and if needed stiffen and better regulate the PSU. Pop the top clear all dust bunnies, check rotation and any worn bearing or just plain noise from the fan. Check to see if the frame enclosure is straight and true. Clean and possibly VERY lightly lube the guides that the left and right edges of the NR card PCB travels on. Make sure the NR card edge finger traces as well as the mating card edge connectors are tarnish, dirt, dust, and gummy residue free. Make sure the NR card seats squarly,snuggly and secure in it's connector. The I/O XLRs get a little tarnished and worn after a while. Consider replacing them with newer Gold Pin connectors if possible.

Once the mechcanical, PSU and connector check/work is done, you may wish to have a general overview look at the components mounted on the PCBs. Most 363 units have been in service for years and with no Power Off switch have been sitting quietly cooking the parts of the rather well populated CAT 300 board(s). Look for swollen or bust electrolytic caps, burn or char marks on the resistors or PCB. Since the 363 is a stereo unit place the cards open side by each and look for any telltale differences between them. It may be advisable to replace the electrolytics with fresh new parts, and with a higher operating tempurature rating than original when possible.

I'm not going to step into the "which cap is best" beartrap. There are others on the forum who have done component level work on these cards and I will defer to them.

Best of Luck with it all.

Cheers!

If anyone could answer a couple of questions about the fan, I would appreciate it.

First, how quiet is quiet for this fan? I just bought a 363 and the fan is making noise. I'm just wondering if they are supposed to be inaudible, or, heck, I don't know, is there a dB standard?

Second, if I do have to replace the fan, what's the generic name for that kind of fan housing? I've never seen one of those in any other piece of gear. If I had to name it I'd probably call it a cowled duct fan or maybe a ducted fan. I just Googled for "ducted fan" and got lots of hits on model aircraft.

Thanks in advance,

JD

[Mark Williams]

Hi,

I like the 363 units and use mine while mixing to my MCI JH-110b all the time. With decent alignment (I favor IEC curve at ref level, 15 ips) the sonics can be great!

My two units both have noisy fans and one seems to be failing. In fact, I have taken to unplugging one when I am not using it, although I think Dolby hardware is happiest when you just leave it permanently powered up. When new these were basically silent but all of them seem to be wearing now.

I did get response from some good folks at Dolby, who have NO replacement parts for 363 units, and traced the original fan maker to an outfit called Micronel. It's a pretty high tech company and they no longer make the correct AC powered model.

However, they do seem to make DC powered versions and my tech and I have talked about getting those and adding a little DC transformer outside the 363 case where it will not effect hum. Here's a link to the Micronel page with possible fan models:

<http://www.micronel.com/e/produkte_axial.asp>

Let me know what you learn, thanks!

Mark

[Paul Gold]

I'd keep looking for another manufacturer that makes a fan that has the right physical and electrical characteristics. Try the usual suspects. Mouser,Digi-Key,Newark,Allied.

[Mark Williams]

It's a funny little cylindrical fan that runs on AC. So far I haven't located one like it but there may be a substitute. My tech has thought about positioning a small fan externally, which we may do, but if I can fix it more like it was originally I'll like it better.

Thanks,

Mark

[wado1942]

I think the fan is a standard 40mm X 10mm, but it maybe worth double checking. The fan doesn't mount to the vent either, but somewhere further inside the units, which doesn't make much sense to me. I'm sure you could get just about any small fan, bolt it to the exterior of the vent and run the wires to the circuit board.

Either way, all I know is that my 363 smells like an unwashed hippie and I've never actually used it on a project in the years I've had it.

DC, do you have any advice on wiring directly to the cards? If I can instal some 1/4" jacks on the back to bypass some extra electronics, that would be great IMO. I've modded both my mix decks to run unbalanced.

[dualflip]

If i remember correctly the main problem comes from the balanced circuit, or transformers in this case, so like DC collins mentioned, the REAl mod is to wire it unbalanced, or maybe change the transformers, anything else wont help very much since the main problem are those trannies.

[Mark Williams]

I believe the 363 uses diff amps instead of transformers, so you may be able to tie in unbalanced beyond those if the impedances match adequately.

The fan sits in a small space between and near the back of the cards, drawing from the front around the cards and exiting through two vents above and below a connector on the back panel. It has a fiber (paper?) tunnel to help direct airflow out the back vents. Since Dolby gear of that period was designed for a continuous duty cycle (no AC switches), I'm sure they were concerned with cooling those crowded cards.

Anyway, I actually use mine all the time and would be glad to hear about alternative fan solutions, thanks.

Mark

[dcollins]

Originally Posted by Mark Williams

I believe the 363 uses diff amps instead of transformers, so you may be able to tie in unbalanced beyond those if the impedances match adequately.

Correct, there are no audio transformers. All you need to do is identify the unbalanced in/outs that go to the Dolby™ card and wire that to the XLR's.

I disconnected the fan on day one and it's been fine.


DC

[Mark Williams]

Thanks!

"I disconnected the fan on day one and it's been fine." that's the best news I've had all day!

Regards,

Mark

[Mark Williams]

I found my note from Dolby re:the cooling fan if anyone is interested (I'm thinking of running without and checking for hot components occasionally myself):

"Hi Mark,

As you mentioned, the Dolby part number for the 363 fan assembly is 83099.

You can contact our sales department: salesadmin@dolby.com to see if you can still obtain it.

Also, here is the specifications for this raw fan:

(FAN 1.42" DIA 3000 RPM 24VAC)

Manufacturer Part Number
MICRONEL A341M-024GK-B

Best regards,

Dolby customer Support"

Mark

[Mark Williams]

I should have added that the sales department said no go on any 363 parts.

[JustDucky]

As Mark posted above, they no longer make the fan in that form factor that runs on AC. Their response...

Good morning. Your request for a Micronel fan has been forwarded to us to address. We are the sole North America distributor for Micronel small precision fans.

Effective June 30th of this year, Micronel ceased production and the taking of new orders for AC-powered fans. The part number you referenced was specifically designed for Dolby and therefore was proprietary in nature and would have been available only from Dolby.

I do not know what to suggest other than possibly looking at an appropriately sized DC fan and utilizing an AC-to-DC convertor. If we can help in any way, please contact us at your convenience.

Best regards,

Vic DeSantis

Micronel Safety USA

12115 Insurance Way

Hagerstown, MD 21740

301 733-2224

301 733-2236 fax

So, I have already been researching plan B. I think the idea of buying the DC product (which will be a D341T/Q, I believe) and using an external wall wart would work fine.

You can look at their datasheet HERE

http://www.micronel-us.com/images/D3...heet_rev_E.pdf

Another option that I've been looking at is buying a 40mm ultra-quiet fan from FrozenCPU and then fixing it to the outside over that weird cutout on the back of the case by drilling a couple of holes into the case and slapping it on with pan-head sheet metal screws. If you do that, you're still stuck with the problem of an external power supply for the fan unless you are adventurous and want to test your luck by cobbling together a little rectifier and filter with a regulator and running off the 24VAC supply that exists. He. I think I'd opt for a wall wart first.

The 40mm fans I'm looking at are HERE
40mm Ultra Quiet Fans | Page 1 | Sort By: Product Title A-Z - FrozenCPU.com

I hope this helps fellow 'slutz with noisy 363 fans.

Cheers,
JD

[Mark Williams]

Great info, thanks! I would feel better keeping those components cool, even though a previous respondent said he's doing fine without that. The external wall wart will add to the snarl in my racks but won't be hard to deal with otherwise.

Has anyone checked on the cost of the Micronel DC version of that fan?

Mark