No voltage at position 18 Mojotone 18watt tmb

dsutton24

Doctor of Teleocity
Joined
Dec 29, 2010
Posts
10,992
Location
Illinois
Your soldering needs a little work in a few spots, but on balance you've done a pretty respectable job on that thing. On the next project you should allow some space between resistors, and also some space between resistors and other components like capacitors and wires. Some of those resistors get pretty hot.
 

Martinoils

TDPRI Member
Joined
Jul 3, 2014
Posts
57
Location
Tucson, Arizona
Your soldering needs a little work in a few spots, but on balance you've done a pretty respectable job on that thing. On the next project you should allow some space between resistors, and also some space between resistors and other components like capacitors and wires. Some of those resistors get pretty hot.
Thank you, much appreciated!
 

Martinoils

TDPRI Member
Joined
Jul 3, 2014
Posts
57
Location
Tucson, Arizona
From reading the earlier post I see that you have reflowed pin 7 on the sockets. Many of your turrets also appear to be lacking solder which could lead to poor electrical contact. If you are having trouble getting good solder joints on the turrets, you may need a larger tip for your iron to help heat them properly.
Thanks I’ll correct that!
 

Martinoils

TDPRI Member
Joined
Jul 3, 2014
Posts
57
Location
Tucson, Arizona
From reading the earlier post I see that you have reflowed pin 7 on the sockets. Many of your turrets also appear to be lacking solder which could lead to poor electrical contact. If you are having trouble getting good solder joints on the turrets, you may need a larger tip for your iron to help heat them properly.
Thanks I’ll correct that
 

Martinoils

TDPRI Member
Joined
Jul 3, 2014
Posts
57
Location
Tucson, Arizona
I'm scoring Andrew a hit. Martinoils, you know which tube is the LTP? Heh, the one that's supposed to have a jumper from pin 3 to 8. :) But that's V3 if I'm counting right.
I’ve been looking at that layout so long I miss everything. Of course that’s V3
I need to take a break but not before I make these corrections tomorrow.
Thanks again!
 

Phrygian77

Poster Extraordinaire
Gold Supporter
Joined
Apr 30, 2016
Posts
5,696
Location
Crawfordville, FL
On the next project you should allow some space between resistors, and also some space between resistors and other components like capacitors and wires. Some of those resistors get pretty hot.

The only thing of concern here is the output tubes' cathode cap. It is right on the resistor. That one should be moved. I don't see any issue with anything else.
 

Paul G.

Friend of Leo's
Joined
Mar 17, 2003
Posts
4,227
Location
Rhode Island
The cathode cap resistor is the cement wrapped 130R all the way on the transformer end of the board.

I don't know if this is related to any of your issues, but the lack of solder on your turrets will lead to a very unreliable amp. Put your soldering iron tip on the top of the turret and component lead. Wait a second or so, then touch the solder to the tip, it'll melt into a blob. After a few seconds, the top of the turret will be hot enough to allow the solder to flow onto it. Quickly remove the tip. You should have a solid connection with the entire hole filled and component lead securely embedded.
 

Martinoils

TDPRI Member
Joined
Jul 3, 2014
Posts
57
Location
Tucson, Arizona
The cathode cap resistor is the cement wrapped 130R all the way on the transformer end of the board.

I don't know if this is related to any of your issues, but the lack of solder on your turrets will lead to a very unreliable amp. Put your soldering iron tip on the top of the turret and component lead. Wait a second or so, then touch the solder to the tip, it'll melt into a blob. After a few seconds, the top of the turret will be hot enough to allow the solder to flow onto it. Quickly remove the tip. You should have a solid connection with the entire hole filled and component lead securely embedded.
Thanks I’ll resolder today. How should the cathode cap resistor be moved? Should it be elevated not sitting on the board or is the cap attached to it too close? Thanks again
 

Phrygian77

Poster Extraordinaire
Gold Supporter
Joined
Apr 30, 2016
Posts
5,696
Location
Crawfordville, FL
Thanks I’ll resolder today. How should the cathode cap resistor be moved? Should it be elevated not sitting on the board or is the cap attached to it too close? Thanks again

Don't worry about it for now. The point was that cathode resistor gets hot, and it will shorten the life of the bypass cap. You want some space between them.
 




Top