Shure M67 Mods

RodC · Post by **RodC** » Mon Mar 20, 2006 5:47 pm

I think you should be able to find one pretty cheap, you may not get a tap for the pilot lamps but the rest is just powered by a center tapped tranny. I'll measure the Voltage if you like.

Paul Fury 161 · Post by **Paul Fury 161** » Mon Mar 20, 2006 5:50 pm

That'd be great Rod. I know a few guys who are a bit more electronics savvy than me, pretty sure between me and them it'd be a goer - if you could get those voltages, that'd rule. If you get a chance - don't put yourself out though, I imagine you have far more interesting things to be getting on with! Lemme know what the tap voltage for the pilot lamp is anyways, might be able to scrounge something from somewhere.

Thanks again!
Cheers,
Paul

RodC · Post by **RodC** » Mon Mar 20, 2006 6:19 pm

I had to do a double take on the schematic because the DC voltage is listed as 34V and the main filter cap is only rated at 40V! They cut that one close.

Oh well, its a common full wave rectifier. The outer winding is around 60V with a center tap of aporx 28V. So if you can find a 240V primary with a 60V CT secondary you will be in good shape. Its pretty small measures about 3" square I would say. The tap for the lamp is 6.5V AC.

I metered them just to be sure. The DC voltage was 36V on the unit I checked out.

Be sure to get yourself a manual, the schematic is pretty complete.

Paul Fury 161 · Post by **Paul Fury 161** » Tue Mar 21, 2006 3:30 am

Thanks Rod, that's great. I better get bidding for a unit now. Thanks again for taking your time to point us all in the right direction here, this thread is cool.
Cheers,
Paul Fury

xhavepatiencex · Post by **xhavepatiencex** » Tue Sep 05, 2006 11:58 pm

has anyone else done this and can comment on how they feel it sounds, im curious about it myself.

RodC · Post by **RodC** » Wed Sep 06, 2006 6:07 am

I'll try to post some clips, but if you look around you can find them pretty cheap. Worth the price just for the parts.

The last couple I did I left channel 1 in the mix bus so it has the gain of the summing amp. Channel one then has 2 controls, the original volume and the master becomes sorta like a master gain.

This way you end up with 1 channel with lots of gain and 3 others that work great on loud guitars and drums.

anthonypage · Post by **anthonypage** » Tue Aug 05, 2008 7:26 pm

Hi,

I've just got my hands on a m67 and had a few questions about the particular unit I have and modding it.

This is what I have :
one
two

This is what I've seen other m67's look like :
one

The main difference I see is that the connections are all male xlrs, even the line out. Has this unit has already had some modifications, or is this a different model?

Any information on this would be great before I open it up and start tearing it apart!

Thanks,
Anthony

RodC · Post by **RodC** » Wed Aug 06, 2008 5:33 am

Welcome to the board!

You have an M67. A lot of old mixers had Male XLRs. This is sorta the era when they were changing to female.

Looks like someone added an XLR for the Line out. Prob not modified too bad. Open er up and see whats inside.

anthonypage · Post by **anthonypage** » Wed Aug 06, 2008 6:39 am

Thanks!

I'll make some female to female cables and let you know how it goes.

Cheers,
Anthony

RodC · Post by **RodC** » Wed Aug 06, 2008 7:04 am

anthonypage wrote:Thanks!

I'll make some female to female cables and let you know how it goes.

Cheers,
Anthony

Have fun, I always drill the damn things out and replace them. That is about as easy as making special cables!

anthonypage · Post by **anthonypage** » Wed Oct 01, 2008 6:48 am

Hi Rod (or anyone else who has done this mod)

I have few questions about your steps I was hoping you could answer:

Step 5. Unbalanced jacks correct? Brown and Ground, Red and Ground, etc.. I'm curious because current xlr line out has green and white wire coming from T5 plus ground.

Step 7. Which lug gets the white wire from input transformer? You say "top lug of R9 (side lug connection not connected to ground)" Which I'm confused about. The top lug seems to be connected to ground (black), middle gets connected to #1 spot on pcb in step 8 (originally orange), and bottom lug is disconnected (originally brown).

Power connection :
There is a power cable attached with the ground plug removed creating a 2 prong plug. Is this unit supposed to be grounded? I'll attach a new plug if it is.

Leaving channel in mix :
I haven't decided if I want a channel in the mixbus yet, but if I decide to, I would leave the blue wire connected in step 2, correct?

Thanks for your help...I'm almost there!

Anthony

RodC · Post by **RodC** » Wed Oct 01, 2008 9:56 am

I dont have this unit in front of me so Im shootin from the hip. If this dont clear it up Ill open one up this afternoon.

anthonypage wrote:Hi Rod (or anyone else who has done this mod)

I have few questions about your steps I was hoping you could answer:

Step 5. Unbalanced jacks correct? Brown and Ground, Red and Ground, etc.. I'm curious because current xlr line out has green and white wire coming from T5 plus ground.

Yes, for the outputs you add they will be TS, I sometimes use TRS and solder the ring and sleeve together so I can use all TRS cables and have a psudo balanced connection (there is a link to a jensen article and some details in my DIY section)

http://beyondsanityproductions.com/inde ... &Itemid=28

anthonypage wrote: Step 7. Which lug gets the white wire from input transformer? You say "top lug of R9 (side lug connection not connected to ground)" Which I'm confused about. The top lug seems to be connected to ground (black), middle gets connected to #1 spot on pcb in step 8 (originally orange), and bottom lug is disconnected (originally brown).

When refering to the top im prob talking about the schematic. You want the wiper of the pot to go to the transistor input and the White wire of the transformer to go to the side lug of the pot that is NOT connected to ground.

anthonypage wrote: Power connection :
There is a power cable attached with the ground plug removed creating a 2 prong plug. Is this unit supposed to be grounded? I'll attach a new plug if it is.

All the ones I have seen are grounded.

anthonypage wrote: Leaving channel in mix :
I haven't decided if I want a channel in the mixbus yet, but if I decide to, I would leave the blue wire connected in step 2, correct?

Correct.

anthonypage · Post by **anthonypage** » Wed Oct 01, 2008 12:02 pm

When refering to the top im prob talking about the schematic. You want the wiper of the pot to go to the transistor input and the White wire of the transformer to go to the side lug of the pot that is NOT connected to ground.

OK, since there's only 1 lug left on the pot I'm going to assume it's the free one. (top has ground, center has wire to 1 spot on pcb)

I may not get to it until the weekend but I'll let you know how it goes!

Cheers,
Anthony

RefD · Post by **RefD** » Wed Oct 01, 2008 12:48 pm

a thought regarding the M67 being used for recording the Woodstock soundtrack: maybe they used a buttload of inline pads (those barrel thingies)?

RodC · Post by **RodC** » Wed Oct 01, 2008 2:36 pm

RefD wrote:a thought regarding the M67 being used for recording the Woodstock soundtrack: maybe they used a buttload of inline pads (those barrel thingies)?

Thats sorta what I assumed....

Images of a "buttload" of metal pads exiting some poor assistant's... run through my head.... Disturbing....

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