New JMP50ish build has begun!!!

[bulatovic]

Hi there guys!

After AGES of thinking what to build, considering options, gathering money and finding places to order parts from, i have finally started my next build, what will hopefully be my main amp!

It's something inbetween JTM50 and a JMP50, maybe more a JMP, as it has a bit more "modern" features than the JTM.

Here are the spec it's gonna have:

-Marstran 1202-118 PT
-Marstran 784-139 PT
-Marstran C1999 Choke
-Ceriatone JTM50 Chassis + Faceplates
-Rectifier switch (stiff/loose): Solid state rectifier/Sovtek GZ34
-Filtering F&T caps:
*Stiff setting: Mains: 64uf, Screens:32uf, PI:32uf, Preamp:32uf+32uf
*Loose setting: Mains: 32uf, Screens:32uf, PI:32uf, Preamp:32uf+32uf
-RFT NOS EL34 pair
-preamp tubes: NOS Telefunken, NOS Philips, NOS RFT and NOS EI 12ax7 - will see which one goes where...
-0.018uf Mustards for preamp and tone stack coupling caps,
-0.039uf Mustards for PI coupling caps,
-Silver Mica caps,
-Alpha potentiometers,
-Carbon film resistors,
-Larry's grounding scheme,
-Lar-Mar PPIMV
-Lead/Bass switch:
1) Split/Shared V1 cathode
2) 33k-500pf/56k-250pf tone stack
3) .68uf V2A cathode bypass cap/none
-100pf bright cap
-470k mixer resistors/500pf mixer bypass cap

here's the schematic of the amp:

http://i671.photobucket.com/albums/vv78 ... wBuild.jpg

[bulatovic]

Turretboard build:


So far i've ordered some parts from the US of A, need to get the rest from Ceriatone, but in the meanwhile i've built the Turretboard - it cost me about $3 and some time which i have to say was fun! - good music and a pint of beer!

I got the board which is a bit thicker (5mm) from what used to be an old main fuse box in a house; outlined the dimensions of the turretboard i need and cut it using a saw, then drilled using a drill bit for metal 3.2mm in diameter:

http://i671.photobucket.com/albums/vv78 ... 50/001.jpg
http://i671.photobucket.com/albums/vv78 ... 50/004.jpg
http://i671.photobucket.com/albums/vv78 ... 50/005.jpg

As you see, i got some copper pop rivets that are going to serve as turrets - not truly Marshall correct, but would do just great!

http://i671.photobucket.com/albums/vv78 ... 50/002.jpg

Using pliers i've removed the rivets from the poles that i've fitted into the holes on the board. Again using pliers to squeeze the bottom of the rivet a bit and make it slightly oval shaped rather than leaving it circular, so it wouldn't fall off from the board when fitted:

http://i671.photobucket.com/albums/vv78 ... 50/003.jpg

Fully turreted it looks like this:

http://i671.photobucket.com/albums/vv78 ... 50/008.jpg
http://i671.photobucket.com/albums/vv78 ... 50/009.jpg
http://i671.photobucket.com/albums/vv78 ... 50/010.jpg
http://i671.photobucket.com/albums/vv78 ... 50/011.jpg

Then came the next part - connecting jumpers across turrets below the board:
http://i671.photobucket.com/albums/vv78 ... 50/012.jpg
http://i671.photobucket.com/albums/vv78 ... 50/013.jpg

Bending component leads and putting the resistors and caps in place:
http://i671.photobucket.com/albums/vv78 ... 50/014.jpg
http://i671.photobucket.com/albums/vv78 ... 50/018.jpg
http://i671.photobucket.com/albums/vv78 ... 50/015.jpg
http://i671.photobucket.com/albums/vv78 ... 50/016.jpg
http://i671.photobucket.com/albums/vv78 ... 50/017.jpg



That's where i got so far, the next step is to get all the resistors from my local shop and put them in place as well, cut the wire to length - then comes the soldering!

Hope you like my cheap DIY board

Stay tuned!!!

[Bierschinken]

Pretty nice work! - but Inter is a no go

Ciao,
- Swen

[BrianH]

Wow, that's DIY dedication!

Brian

[bulatovic]

Pretty nice work! - but Inter is a no go

Ciao,
- Swen

Thanks Swen, don't worry it was Inter vs Milan match, i went with the other side

Wow, that's DIY dedication!

Wow, that's some serious praise, coming from the turretboard captain of this forum! Thank you so much!!!

Brian

I'm really enjoying this build, even tho i'm at 3% out of 100% to complete this thing...
Really like the way this board is turning out - even with no solder i get perfect conductance between the turrets connected by jumper lead below the board! It seems that it's going to be a rock solid one!
Can't wait to put some mixture of tin and led and some flux there

Oh, well i forgot to mention that this is my take on Marshall's late '69s, '70s and early '71s boards:

http://www.amparchives.com/album/Marsha ... llbox5.jpg

http://www.amparchives.com/album/Marsha ... 3682_3.jpg

Wow, it just got to me that i should have jumper leads on top of the board, not below! Well, great, another thing to fix before soldering

Thanks again guys!
Hopefully, there's gonna be some progress tomorrow!

[bulatovic]

Next Step: - wires in place, and as said earlier, jumper leads moved from the back of the board to the top

http://i671.photobucket.com/albums/vv78 ... 50/020.jpg
http://i671.photobucket.com/albums/vv78 ... 50/021.jpg
http://i671.photobucket.com/albums/vv78 ... 50/022.jpg
http://i671.photobucket.com/albums/vv78 ... 50/023.jpg



Soldering goes today! Wooo-hooo! can't wait!
Only i'll need to clean the rivets with some alcohol, and with a bit of flux it'll go like a dream!

Stay tuned!

[bulatovic]

Update:

I've been playing with my soldering iron, and this came up:

http://i671.photobucket.com/albums/vv78 ... ic/024.jpg
http://i671.photobucket.com/albums/vv78 ... ic/025.jpg
http://i671.photobucket.com/albums/vv78 ... ic/026.jpg
http://i671.photobucket.com/albums/vv78 ... ic/027.jpg
http://i671.photobucket.com/albums/vv78 ... ic/028.jpg
http://i671.photobucket.com/albums/vv78 ... ic/029.jpg

I admit, it's not the neatest job ever, but it works just fine. The problem is with soldering on those copper "turrets", you really have to get those buggers hot before you can put some solder on. It was rather tricky to make those nice balls on top of the turret where the component is soldered to, but overall, i'm satisfied! I'll redo some of the joints when i get the rest of the components and finalize the board. There's some excess solder on some turrets where the wire wraps around, will sort that out as well

Oh, yeh - AC/DC vinyls - yep, that's what this amp is mostly going to play :

Now, i've reached the point of waiting...
Some parts from USA are arriving - well all the parts that i'll need on the board, and i'm about to order the rest from Ceriatone - so hopefully in a week or so i'll have some other stuff to add to the amp :

Thanks for viewing!

[arledgsc]

Nice specs and inspiring build. Try a little solder flux on those copper turrents. Not the acid flux used by plumbers but something intended for electronic assembly. You will be amazed how easy it will be to solder.

I used a Ceriatone JMP/JTM50 chassis on my JTM50 build. The -184 Marstran OT and Mercury PT are slightly closer together on this chassis versus the Metro JTM45. As a consequence and perhaps by chance I get a very small amount of low-level hum from the loudspeaker when the Mains are On but not necessarily the HT standby. I get the same amount of hum with tubes or no tubes including the rectifier. Pulling my hair out I rewired my amp and hum still present. The problem boils down to the OT and PT are coupled magnetically. Moving the OT away slightly would be a major pain and last resort. I finally have a solution that I can live with and that is a 2" wide mu metal ring slipped around the PT. The hum is knocked down to background levels. Anyway not trying to be an alarmist but something to be aware of on your build. Maybe I have a bum transformer so I would be interested if you have a similiar issue with your Ceriatone chassis. Funny my Metro chassis JTM45 with the same Mercury PT and -103 Marstran OT is ultra quiet. Both amps have Larry ground.

Best of luck and this is going to be a stellar amp. I recently installed some KT77s in the JTM50 and OMG it sounds great with a Strat and rivals my beloved JTM45. I don't know which amp I like best at this point! Scott

[bulatovic]

Hey Scott,

Thanks a lot mate!
Well i hope that it's gonna be as good as it seems to be on the paper
Thanks for sharing your experiences with the PT/OT positioning! I'll try with the existing holes, but if that turns out to be really hummy, i might do the headphones trick to reposition the OT. But, hey, when you crank it up, u hear nothing but pure awesomeness, no hum
As for soldering, well i did use flux paste, but it really didn't help all that much.
I've tested each and every joint 3 times so far, each connection to make sure i read less than 1ohm resistance between the lead of the component (nearest possible point to the component) and its wire end where it's gonna connect to a socket/pot/input or what have you, and everything seems just fine.
Though, if anything turns out to be a bit crackly or hissy it'd be those NOS CC 470k mixers, as they read 454k already, but they might work just fine...

Getting nervous with waiting for the parts to arrive
can't wait to proceed with the build!

Luka

[bbaug14]

Did this build ever get finished? Has anyone implemented this diode/tube rectifier switch with success? I'd really like to use this in my next build but I'm curious if anyone had issues with it. Thanks!!!

[Haze13]

Mesa Boogie "Dual Rectifier". The name of a model says it all. All the schemes are in the Internet.

[ivan H]

Hi bbaug14, yes I have used a switchable rectifier/main filter with success. I used a 3PDT switch from Valvestorm. I did post on here somewhere about it. U will need to use a bias supply dropping resistor when in tube rectifier mode so that the output tubes are correctly biased in both solid state & tube rectifier modes. I wired the resistor directly to the switch so that the switch shorts the resistor in SS rec mode, supplying full AC voltage to the bias network. When switched to tube rec, the AC supply goes thru a 15k resistor then to the bias network, which in my case keeps the output tube bias within 1mA in both modes. Hope this helps. Cheers

[emmjaydubya]

Here are a couple of threads started by Shakti where he did this on his excellent JTM50 build. The first one is rather short but has pics:

http://forum.metroamp.com/viewtopic.php?f=7&t=38611

Half way down the second page of this next thread, after alot of experimenting, playing and burning in, he comes to the conclusion that changing up the B+ on the switch (depending on your PT of course) with rectification and biasing on each side was the most beneficial for each type of rectifier. Really good stuff!

http://forum.metroamp.com/viewtopic.php?f=24&t=38617