The title says it all. This is a Hybrid-A based off of Normster's layout. I believe the issue is with the reverb?
Here are the stats:
B+ 1 467, 2- 458, 3- 449, 4- 362, 5- 360
As you can see the wiring is screwed up at Tube 3 and possible 4. I am using a reverb tranny from Lord Valve ( a fender replacement) and have it hooked up as follows:
Blue to pin1
Green to RCA
Red to b+2 ( on Bias board- Red to white wire)
Black to ground at power tube ground.
Other red wire is RCA to pin 7.
Any ideas?
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Last edited by keithrick on Sun Jun 04, 2006 7:25 pm, edited 1 time in total.
Thanks for the reply Norm, I tried the amp without the reverb tube and still no sound. When I probed the PI the voltages were still at B+3 (around 446) at pin 1 and 6 almost like the resistors didn't drop the voltage at all. However, I did here sound when probing!
My main concern is that I have the reverb transformer hooked up incorrectly. I am going to recheck my wiring again now that I have a fresh perspective.
It's a little hard to tell from the pictures, but it looks like you don't have a connection from the phase inverter tail to ground (or to the presence control). That would explain the voltage readings you're getting. That would certainly break the audio signal.
Dave
Keith, as you continue probing from the PI towards V1, you should here some noise (albeit, diminished). If you get to a part of the circuit where you hear nothing, you've pretty much got it isolated.
I can't tell from your pics, but make sure the resistor that goes from the PI to ground is a 4M7. If you've mistakenly used a 4k7 it will send your signal to ground.
To eliminate the reverb circuit as a suspect, just unsolder the wires that run from the pot to the board. The 2 things that I would be most suspicious of are heater wires and the channel switch. If you got the ground connection reversed on the channel switch, it'll ground your preamp signal. If the heater wires have a bad connection, you won't get enough heat to the cathode to emit any electrons. (I had that happen on my first build. All pins had the correct voltage but V1 wasn't glowing. Turned out to be a loose sleeve in the tube socket.)
I like to go step by step through the gain stages.
Connect a blocking cap to a test lead. connect this test lead to the input of another amp. I use my stereo but a guitar amp will do too. Connect the input grounds of both amps together with another test lead.
Inject a signal at the input, like a CD player.
Now take the test lead and connect it to the grid of V1a to verify the signal.
Next connect the test lead to the plate of V1a. You should have a louder signal.
Continue through the entire amp this way until you find where the signal is lost. This will naoorw down your troubleshooting.
Hope this helps. My voltages are not dialed in, but the amp works and sounds pretty good. From the looks of your readings, your problem is most likely with the PI, not the reverb.
bluefireamps wrote:It's a little hard to tell from the pictures, but it looks like you don't have a connection from the phase inverter tail to ground (or to the presence control). That would explain the voltage readings you're getting. That would certainly break the audio signal.
Dave
Yup, I think you're right. Let's hope Keith comes back to check this thread soon.
It's a little hard to tell from the pictures, but it looks like you don't have a connection from the phase inverter tail to ground (or to the presence control). That would explain the voltage readings you're getting. That would certainly break the audio signal.
Dave
Thanks I am here, come to think of it I am here alot! You are right I just noticed that from the presence control to the 4K7 resistor is fine but it is not connected to the 24K tail. DUH!!! I will fix and report back!
Well I fixed the ground of the presence and I have sound. But I have other issues to figure out. The switches work except for the channel select switch.
I get a distortion very high gain but....It is only controlled through the Master, I can't tell if it is the Clean channel maxed or the OD channel none of the controls effect sound Back to the wiring schematic.
One question: When using Norms layout are you grounding exactly like it is on the layout, i.e., the only ground on the tone controls and switches is the 10K on the deep switch?
Looks like another couple of errors on my schematic. The mid pot wiper (center lug) should go to ground and the volume pot ccw (left lug looking from the back) should also go to ground.
I noticed the missing grounds on Normster's schematic and thought he'd
hadn't drawn them in as they were a given. I always try to draw my own
layouts from schematics, that way one becomes familiar with the ckt and can compare the good,bad,ugly of others's layouts. It's amazing how many mistakes you can find in your own layouts though 'fresh' eyes the next day.
Here are some pics of my "Rats Nest" wiring of the controls. I added the grounds to the Volume and Mid pots and now have more control, all the switching works other then the channel. I have attached some more pics for your viewing pleasure
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pin3 2.654
However, I did here sound when probing! 
Back to the wiring schematic.
