Rather then continue the original thread I thought it better to start a new one since this project is about to take a drastic change in direction. It was mentioned the layout is poorly done and being a student I take that as constructive criticism. So that is the first area to improve- Not looking forward to it since moving some wires may not be the simplest route, can I get away with just rerouteing the wires? The grid resistors on the power tubes are not right up against the socket terminal. In fact there is about a 1/2 inch of lead on both sides.
There is still an underlying 60 hz hum that does not increase with volume but being a power amp only, really shouldn't be there. Regarding the hum, I have (2) tube sockets wired with no tubes in them, could it be that? The ground on the bias circuit was never really made perfect as there was no lock washer on the screw that held the solder lug to the chassis. The chassis is steel, I've heard that too can be a source of hum.
Other suggestions on cleaning up the wiring?
After I get these areas corrected I'll post the JTM-45 preamp schematic I'll be working from and post some questions regarding that phase.
Thanks all for any assistance,
silverfox.
Sceptre-45 Build, in progress...
Moderators: pompeiisneaks, Colossal
Sceptre-45 Build, in progress...
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Well it's Up and Running
I ended up rebuilding the whole, (just about), amp. I know the wiring is not the best however there are no oscillations or crossover noise so at some point I'll tie wrap the wires together and that should clean up the Rats Nest.
The Good: Very quiet, I mean to say no background noise. At all! With the exception of when the Boost switch is engaged. I'm beginning to think the design on that FB circuit is poor so I'll change over to a classic Presence circuit. It sounds like a JTM 45, substantially.
The Bad: It don't take an amp emulator very well at all. The lower frequencies are being filtered out and the sound is tinny and perhaps over driven in a bad way. I've got to rewire the MV since it is backward.
The Ugly: One channel does not sound like the other. The high frequencies are cut. I didn't use the 4 input jack model and neither are the jacks wired for a high and low gain input. The reason for that is, with an emulator and distortion box, ect.. I figured the 68K input should be sufficient. Another huge problem is: The tone controls have just about zero effect on the tone. It does get a nice overdrive grind and with the gain I can get good FB with the guitar but essentially this has a ways to go and here is the first request for proposals I guess you'd call it.
Before I go too far I should also specify, I like the sound of the channel that works, (of course tone controls would be nice too). What I think I'm going to do at this point is strip out the second channel and rewire that for a simple tube input with no real gain so that I have a effects box input.
There is a very good chance I'll rebuild the circuit again from nearly scratch, Not sure yet. All constructive criticisms is appreciated. epis commented the layout and wiring were not done well and I took that as an area to improve on so feel free. Hope the wiring turned out better this time.
silverfox.
The Good: Very quiet, I mean to say no background noise. At all! With the exception of when the Boost switch is engaged. I'm beginning to think the design on that FB circuit is poor so I'll change over to a classic Presence circuit. It sounds like a JTM 45, substantially.
The Bad: It don't take an amp emulator very well at all. The lower frequencies are being filtered out and the sound is tinny and perhaps over driven in a bad way. I've got to rewire the MV since it is backward.
The Ugly: One channel does not sound like the other. The high frequencies are cut. I didn't use the 4 input jack model and neither are the jacks wired for a high and low gain input. The reason for that is, with an emulator and distortion box, ect.. I figured the 68K input should be sufficient. Another huge problem is: The tone controls have just about zero effect on the tone. It does get a nice overdrive grind and with the gain I can get good FB with the guitar but essentially this has a ways to go and here is the first request for proposals I guess you'd call it.
Before I go too far I should also specify, I like the sound of the channel that works, (of course tone controls would be nice too). What I think I'm going to do at this point is strip out the second channel and rewire that for a simple tube input with no real gain so that I have a effects box input.
There is a very good chance I'll rebuild the circuit again from nearly scratch, Not sure yet. All constructive criticisms is appreciated. epis commented the layout and wiring were not done well and I took that as an area to improve on so feel free. Hope the wiring turned out better this time.
silverfox.
You do not have the required permissions to view the files attached to this post.