Mojotone JTM45 Schematic in Emailable Form?

[The New Steve H]

These guys can help you more than I could ever hope to, Steve. Glad you made it.

[ToneMerc]

I'm the Vet/newby/PITA that's been buggin' the NEW STEVE H about this amp kit. I guess the real problem is that I have NO INSTRUCTIONS & only my limited electronic skills to go on and don't want to blow up or otherwise incinerate this kit I've waited so long to get. The little bit I think I know about the 45 is that it uses KT66s (?) and my kit came with EL34s. Both OT & PT are labeled "JTM45" but there's mention of a 1987 circuit. So I really only have my gut and the guts of others to go on.

Hi Steven, what circuit documentation was included with the kit? I was confused too when looking at the Mojo website and as to which circuit parts are included. As far as build instructions it doesn't get much better than the MetroAmp instructions.

http://www.metroamp.com/downloads/JTM_45_KIT_V2.1.pdf

Mike

[M Fowler]

Well I stand corrected

The quality of the mojo garolite boards is terrible, board chipped, not cut straight, and turrets were not in straight line (where they should have been), so I used my own.

Sure it would have functioned but if your going to build an amp, do it well and looking good is important too.

Mark

Andrew from Mojo called and emailed me about their JTM45 boards and they are very nice, build quality is great and good product.

As you can see they stand behind their product enough to send me a new board. Thanks Mojo.

Mark

[steven21042]

maybe I'll call this the "JTM48".. Steve H..you look better than I've ever seen you by the way . As far as circuit docs Merc these 3 documents came with the kit:
1 Schematic
1 Layout
1 Materials list

I've perused both the Metro 45 & 50 instructions for weeks and both seem different from my kit which adds to my confusion. I managed to find the following Harmony Central forum pages which partially document my EXACT KIT build.



http://acapella.harmony-central.com/sho ... structions.


http://acapella.harmony-central.com/sho ... TM45-Build



These forum guys (about 15 anyway) all bought the same Mojotone JTM45 kit back in '09 and built the kits "online " with step by step instructions from 2 of the more experienced members. GREAT stuff but not geared for the "early numbskulls" like myself. Some of the more obvious, more elementary steps were omitted. Additionally, since 2 yrs. have gone by the current "JTM45" kits , at least mine, seem to be slightly different due to component upgrades.
Some of my concerns are the underboard wiring connections and the buss grounding locations for the pots..which pots get grounded AND do they ground to the left pins or to the pots' bodies?
I've messaged the two guys who "ran" the build but I guess it's been so long ago and I appear to be the newest, biggest dummy in the forum that I haven't gotten any replies back...

I was worried after reading some of the posts here concerning Mojo's track record with too-small resistor leads and less-than-acceptable turret boards. I was pleasantly surprised then when Andrew sent Fowler a replacement board.

Steven

[ToneMerc]

I'm at work so links and pic downloads are blocked. However,if thats the same thread that someone posted earlier, I drew the conclusion that the thread built kit was a special forum group buy from Mojo and wasn't necessarily the same kit that is currently posted online.


All JTM45 circuits are the same, so the instructions are universal. If your kit parts doesn't seem to match Metro's instructions or part layout, then maybe you do have 1987 circuit parts with JTM45 trannies.

A JTM50 is a JTM45 circuit board with either a tube or s/s rectifier and a dual 32uf board cap instead of a single 16uf and of course it has EL34 tubes and OT.

From looking at the current Metro ad and parts displayed, it seemed like a 1987 circuit with a tube rectifer .

TM

[steven21042]

I'm hoping that I don't offend anyone with my comments or posts. I know they must appear so basic as to be boring....but....I noticed that the Metro 45 has 1 16UF can Filter cap and 1 32UF can Filter Cap. My Mojo "45" has 2 32 UF can Filter Caps. The Metro has a rather large 16 UF cap smack dab in the middle of the board where my kit has natha...Are there any 1987 circuit layouts available for perusal and study???

[ToneMerc]

I'm hoping that I don't offend anyone with my comments or posts. I know they must appear so basic as to be boring....but....I noticed that the Metro 45 has 1 16UF can Filter cap and 1 32UF can Filter Cap. My Mojo "45" has 2 32 UF can Filter Caps. The Metro has a rather large 16 UF cap smack dab in the middle of the board where my kit has natha...Are there any 1987 circuit layouts available for perusal and study???

[steven21042]

Is the 1987 circuit different then the JTM50? .....I suppose I could try & build my kit according to the Layout provided I just don't have any real experience figuring out which wire goes where. I can't even see a ground buss across the pots on the diagram.

[The New Steve H]

I wouldn't sweat too much about dumb questions. I think most people here appreciate your service and are glad to be able to do something for you in return.

[M Fowler]

Here is another layout which you can use for the mojo JTM45 kit as well.

[steven21042]

I notice that there are different color wires on the turretboard. Do these colors represent wiring connections such as ..black to ground, purple to pots , reds to something else? I'm guessing that the colors will simplify troubleshooting later.

[ToneMerc]

I notice that there are different color wires on the turretboard. Do these colors represent wiring connections such as ..black to ground, purple to pots , reds to something else? I'm guessing that the colors will simplify troubleshooting later.

Steven there is a wiring standard, but for all practical purposes one could use only color if one wished to do so. You are correct, it does make troubleshooting that much easier.

This link is close to an old radio wiring standard chart that I have.

http://diyaudioprojects.blogspot.com/20 ... -code.html

Mike

[steven21042]

So, if the EL34s make this kit sound like a JTM50 what exactly does the tube rectifier bring to the party? I know the Metro 50 Plexi has a bridge rectifier. Does the tube rectifier serve then as the bridge rectifier?

[ToneMerc]

So, if the EL34s make this kit sound like a JTM50 what exactly does the tube rectifier bring to the party? I know the Metro 50 Plexi has a bridge rectifier. Does the tube rectifier serve then as the bridge rectifier?

http://vintageamps.com/jtm50/

[Reeltarded]

The transitional 50 with a tube recitfier is my second favorite Marshall. Not umm.. smergy like the 45. Squatty, forward, gritty.