yamaha pm-400 8 channels recap (pm-1000 little brother)

[Vyvyan]

im recapping a yamaha pm-400 (service manual attached) its basically a simplified 8 channel pm-1000, but the coupling caps are quite different. i plan on replacing with wima 3.3 polys. the coupling caps to the output amps are .022 which is much lower than the pm-1000 even though its the same amp with the same component's, should i replace with a 3.3 wima aswell?

also i have three pm-1000 modules and a master module, planning on using the extra gain blocks from those modules as amps for selectable direct outs with 600:600 transformers and possibly replacing the pm-400s baxandall eq with the inductor eq from the pm-1000 and adding a line in transformer (10k:10k???) and possibly adding a second echo or foldback send (i have a surplus of parts so money isnt an issue)

any help with coupling values much appreciated. all suggestions welcome

 

[Vyvyan]

Bump, here's a photo for those unwilling to download pdf

 

[hageir]

Have you looked at the PM-430 service manual? Might find some hints there..

 

[Vyvyan]

Have you looked at the PM-430 service manual? Might find some hints there..

i have the 430 service manual somewhere, ill compare 2, thanks. I also have two other yamaha consoles im using for parts, an m916 and m512 along with a couple old allen & heat 70s discrete mixers. currently building 2 consoles with their parts and other vintage parts ive collected, a 12 channel api inspired desk with the A&H parts and 12 channels with the pm100/400 parts.it's a bit overwhelming, but its a great learning project and its coming along quite well so far, ill share the finished builds when done. Any ideas/info is greatly appreciated

 

[stevegkeezer]

im recapping a yamaha pm-400 (service manual attached) its basically a simplified 8 channel pm-1000, but the coupling caps are quite different. i plan on replacing with wima 3.3 polys. the coupling caps to the output amps are .022 which is much lower than the pm-1000 even though its the same amp with the same component's, should i replace with a 3.3 wima aswell?

also i have three pm-1000 modules and a master module, planning on using the extra gain blocks from those modules as amps for selectable direct outs with 600:600 transformers and possibly replacing the pm-400s baxandall eq with the inductor eq from the pm-1000 and adding a line in transformer (10k:10k???) and possibly adding a second echo or foldback send (i have a surplus of parts so money isnt an issue)

any help with coupling values much appreciated. all suggestions welcome

I am about ready to do a recap of this same unit. Was curious what eqs and caps you ended up going with and if you liked the results.

 

[Vyvyan]

I am about ready to do a recap of this same unit. Was curious what eqs and caps you ended up going with and if you liked the results.

still in the process, have one channel with some wima 3.3uf for coupling and a couple decently sized 4.7uf polypropylene caps i have. electrolytic not in audio path are replaced with original value nichicon fine gold, and vz series for power decoupling. it sounds great so far, but im gonna experiment with some values. havent touched the eq yet but i have quite a few spare inductors laying around so im thinking of adding a insert after after the mic pre and doing a simple passive eq post insert something like an api 553, ill post updates soon

 

[Vyvyan]

I am about ready to do a recap of this same unit. Was curious what eqs and caps you ended up going with and if you liked the results.

heres a little info i just got


"As for the pm400, it’s a sweet little console. I have one that I modded years ago to have direct outs that were post-EQ. I recapped it as well. The only thing tricky about recapping this one is that it has a bunch of bipolar electrolytic caps. They are labeled “BP”, but otherwise look similar to the rest of the caps. Go 5x to 10x bigger on replacement cap values over stock as long as they will physically fit in there. Replace the tantalum and film caps with some Wima or Kemet film caps."

 

[Vyvyan]

heres a little info i just got


"As for the pm400, it’s a sweet little console. I have one that I modded years ago to have direct outs that were post-EQ. I recapped it as well. The only thing tricky about recapping this one is that it has a bunch of bipolar electrolytic caps. They are labeled “BP”, but otherwise look similar to the rest of the caps. Go 5x to 10x bigger on replacement cap values over stock as long as they will physically fit in there. Replace the tantalum and film caps with some Wima or Kemet film caps."

pretty sure the person i got this info from is speaking on the pm-430 not the pm-400. I think ill just end up following suggestions for the pm-1000 as they are basically the same circuits and theres and abundance of pm-1000 info. pm-400 is quite a rare bird

 

[stevegkeezer]

I luckily just scored a pm-1000 with 6 channels. Internals look pretty good. Someone had removed all the tamura output transformers from the master bus channels. Luckily the guy included 3 as spare parts. I bought another scrap master channel on reverb that included 3 more transformers. So I think I am going to wire up the two master channels and recap them. Then recap all the individual channels.

Think I am going to leave the pm-400 as is for now. I agree it's very hard to find any info on those units compared to the pm-1000.

 

[Vyvyan]

So, im planning on replacing the input load switch and resistors with a simple pot for variable input. wanting to use it clean, but also have the ability to send it into fuzz territory and adding a DI in switching jack between the transformer and input pot.

what would the optimal pot value be! 4K7? 10K? 25K? would a switchable input pad pre transformer be a good idea aswell?

also i'm planning on bypassing the fader adding a transformer balanced 10K:10K line input into the EQ and reworking the echo send into an insert point with the return coming back to the line transformer noted above, should i have the insert send tapped straight from the 10k pot? would 47K be a better choice? or should i use the two transistor echo amp as its is for the send? terminating with a 47K or 10K instead of sending it to the echo out amp?

Im not doing any summing so im repurposing the line and echo output amps for direct outs on all channels, 8 in 8 out and putting a fader before the final line amp. not sure how the summing of the original circuit really works. for the direct outs could i scrap the 47k summing resistors and use a 10K fader in place of the 25k fader in the original summing circuit, before the final output amp?
and would i need the change the feedback resistor of the final amp since im going direct out with no summing?

i also have a few pm-1000 input and 1 talkback module (same gain blocks as the input channels) im using for parts, should i just copy those gain blocks instead? i know the pm-1000 runs on 44v and this board is 34v, so would that cause problems? i have a 44v linear supply maybe i should use that for the output amps?

i know the gain of the input amp is set by the 10k resistor in the feedback, i would like to either replace with a 25K pot or a stepped attenuator, but id have no idea of resistor values for that.

btw already recapped with higher value electros and all coupling cap are 5uf polycarbonate film and i plan on using a 470uf panasonic fc on the output into 600 ohm 1:1 transformers. and have replaced most of the 2sc1000's with mpsa18's

all recommendations are welcome and much appreciated.

thanks
and sorry, i know the schem is blurry in the photo above ive attached better ones in two parts, or you can view the original pdf in the first post its crystal clear!

 

[rjb5191]

Any updates? I'm thinking about getting one of these boards.

 

[johnny free]

I luckily just scored a pm-1000 with 6 channels. Internals look pretty good. Someone had removed all the tamura output transformers from the master bus channels. Luckily the guy included 3 as spare parts. I bought another scrap master channel on reverb that included 3 more transformers. So I think I am going to wire up the two master channels and recap them. Then recap all the individual channels.

Think I am going to leave the pm-400 as is for now. I agree it's very hard to find any info on those units compared to the pm-1000.

View attachment 91655

I am about ready to do a recap of this same unit. Was curious what eqs and caps you ended up going with and if you liked the results.

I luckily just scored a pm-1000 with 6 channels. Internals look pretty good. Someone had removed all the tamura output transformers from the master bus channels. Luckily the guy included 3 as spare parts. I bought another scrap master channel on reverb that included 3 more transformers. So I think I am going to wire up the two master channels and recap them. Then recap all the individual channels.

Think I am going to leave the pm-400 as is for now. I agree it's very hard to find any info on those units compared to the pm-1000.

View attachment 91655

Do you still have the pm400? I am looking to buy one.

 

[stevegkeezer]

Do you still have the pm400? I am looking to buy one.

I do

 

[stevegkeezer]

I would be willing to part ways with it.

 

[johnny free]

What would you want for it?

 

[stevegkeezer]

I was hoping to get about 300 for it. I am open to trades for other audio gear as well.

 

[johnny free]

I just stumbled upon your reply this morning, i wish i saw your reply right away! Is there a way to send a direct message through here?

 

[stevegkeezer]

I just stumbled upon your reply this morning, i wish i saw your reply right away! Is there a way to send a direct message through here?

Just sent you a DM