New, First Build 18 Watt Marshall Clone No Sound.

[gtrplayr1976]

Hi folks,

I have my Twin repair on hold waiting for parts , so I was finishing up my 18 watt Marshall clone from Mojotone. This is what I've done. First time I powered it up I used a light bulb limiter. Everything seemed fine. I could barely see any light. I then powered it up without the limiter. No smoke, sparks. Everything lights up, but there is no sound. The 2x12 cab is new. I had doubts about the wiring for the speaker outputs ,so I rewired it by another kit (Tube Depot) ,and it blew the fuse as soon as I powered it up.
I changed the wiring back ,and I will have spare fuses this evening when I get home. I checked through the wiring while it was off ,and found one ground wire not soldered. I'm not sure if this was the issue ,but definitely AN issue ,so that was fixed. I didn't get voltage readings , but will this evening if I can keep it on long enough. I will post the schematic ,layout , and gut shots. I may have missed some wiring/jumpers somewhere. I got kind of snowblind after awhile
Thoughts ,and opinions mean a lot to me on this forum. You guys really know your work.

Thank you

[gtrplayr1976]

Ya know, I was just looking at the gut shot ,and the layout ,and there's a possibility I missed some ground jumpers that connect to the 2.2K resistor at the top of the board unless I put them on the bottom. Geez...what a maroon.
So now I see another omission in wiring. Pin 3 on the power tubes isn't wired. I need to get this corrected ,and post back with issues I may have after I correct everything I've found. This is embarrassing

[gtrplayr1976]

OK, Here is what I did last night. Got the wiring straight I think. I did find the red wire from the output tranny connected to the wrong side of the can. (At the time I didn't think it matted which side.) When I powered it up I checked the power tranny voltages. Yellow/white 6vac , heaters 6.8 vac, the two red wires had 315 vac on each to ground. I forgot to write down the voltage across them. I also noticed that now the preamp tubes were not lit up. Power tubes ,and rectifier tube were all lit. I think they sent me the wrong tubes also. Didn't notice that until I looked at one of the boxes (with my glasses this time) They sent E88CCs. Aren't these for stereos ,and why aren't they powered now ? There are no test points shown on the layout ,or schematic ,so I'm really not sure what to check.

[g1]

They sent you the wrong tubes, contact them and get the right ones. Maybe someone thought they were ECC83's. The mojo kit is supposed to ship with 12AX7's.
You could rewire it to use the E88CC's, but then you need to use them all the time.
The nice thing about wiring it up for 12AX7's is you can try so many different tube types that use the same wiring but sound a bit different.

[big_teee]

Hi folks,

I have my Twin repair on hold waiting for parts , so I was finishing up my 18 watt Marshall clone from Mojotone. This is what I've done. First time I powered it up I used a light bulb limiter. Everything seemed fine. I could barely see any light. I then powered it up without the limiter. No smoke, sparks. Everything lights up, but there is no sound. The 2x12 cab is new. I had doubts about the wiring for the speaker outputs ,so I rewired it by another kit (Tube Depot) ,and it blew the fuse as soon as I powered it up.
I changed the wiring back ,and I will have spare fuses this evening when I get home. I checked through the wiring while it was off ,and found one ground wire not soldered. I'm not sure if this was the issue ,but definitely AN issue ,so that was fixed. I didn't get voltage readings , but will this evening if I can keep it on long enough. I will post the schematic ,layout , and gut shots. I may have missed some wiring/jumpers somewhere. I got kind of snowblind after awhile
Thoughts ,and opinions mean a lot to me on this forum. You guys really know your work.

Thank you

FWIW, I always put the Strapping wire on top of the turret board.
I put the wires flat on the board, and run the components, raised by the turrets over them.
I learned that from the Metro Instruction booklets.
It makes chasing the B+ and Grounds when trouble shooting much easier.
I use one color for the B+ and another color for the grounds.
You can try that on your next build, if you want to.
T

[gtrplayr1976]

Thanks big_teee. So you connect the wires to the bottom of the turret lug ,but on top of the board ?

[gtrplayr1976]

They sent you the wrong tubes, contact them and get the right ones. Maybe someone thought they were ECC83's. The mojo kit is supposed to ship with 12AX7's.
You could rewire it to use the E88CC's, but then you need to use them all the time.
The nice thing about wiring it up for 12AX7's is you can try so many different tube types that use the same wiring but sound a bit different.

I have contacted them. He tells me they don't even sell the E88CCs , So I have to send pictures of the boxes ,and tubes. Geez...

[g1]

So you connect the wires to the bottom of the turret lug ,but on top of the board ?

Yes, I believe this is what big_teee meant, it will make troubleshooting much easier when required.

I have contacted them. He tells me they don't even sell the E88CCs , So I have to send pictures of the boxes ,and tubes. Geez...

Then whoever is supplying them must have sent E88CC instead of the ECC83/12AX7 that they specify: 18 Watt Vacuum Tube Kit (2220002) - Mojotone.com
They should be happy you are informing them of the problem, the longer it goes on, the bigger the headache for them. If they don't just tell you to keep the "wrong" ones, and send free correct ones, then they should be the one's paying for return shipping.

[gtrplayr1976]

Yes, I believe this is what big_teee meant, it will make troubleshooting much easier when required.


Then whoever is supplying them must have sent E88CC instead of the ECC83/12AX7 that they specify: 18 Watt Vacuum Tube Kit (2220002) - Mojotone.com
They should be happy you are informing them of the problem, the longer it goes on, the bigger the headache for them. If they don't just tell you to keep the "wrong" ones, and send free correct ones, then they should be the one's paying for return shipping.

That's my guess too g-one. I think he was a little puzzled when I emailed him. I payed absolutely no attention to them when I installed them. I just happened to look at one of the boxes ,and it caught my eye.

[gtrplayr1976]

I have the 18 watt all fixed ,and running pretty well after a few minor changes. Moved a few ground wires to get rid of some hum ,changed the cathode bypass caps to a smaller value to fix the muddy/fuzzy sound. It has been a true learning experience. Now time for a new project ! JTM45 !

Thanks Folks !