I installed a mini switch just below the "Tweed" switch and coupled a 100pF brigt cap to it.
Allthough it is still no Vibrolux, the accute need for one dissappeared in an instant. This mod takes it a long way into Deluxe Reverb territory - and then some. I´d say this mod is almost mandatory!

Not much happening in here, but I give a shot  

I'm really enjoying my Prinzetone, but sometimes miss a more Vibrolux kind of tone.
I'll try a bright cap to get a little more sparkly treble at low volume.

Does anyone  have other ideas for usefull mods?

If only one could put in one 6L6 and pull the other tube... Low wattage Vibroverb in an instant...  

Would the transformer be able to handle 6L6 tubes (rebias offcourse and then use an attenuator) to take the sweetspot volume down)?

Guess this is of very little interrest to anybody, but anyway:
The scraping/scratching that was pretty annoying the first seconds/minute or so, suddenly just dissappeared and never came back. I suspect dust of some kind inside a pot that didn't go away until the amp was used for a while. Now it is 100% - and then some.
Great amp!

Good advise to turn off the vibro 
Think I'll add a grounded point as well, as the chassis is painted.
Another bias pot would be a good idea actually, but where to run the wires then (goes to the last22k 1w resistor on the main board as is)?

I was thinking about installing external bias check points on my Prinzetone.
It is as easy as running wire from pin 8 on a powertube to red point and from grounded end of 1R2W resistor to black point, right?
Also: Is there any need for running red wire from pin 8 on both tubes btw?

Hey,
Only good vibrations 
The NFB control does not make a lot of difference. Very little actually.

Thanks!
The powercable is a DIY made of 3 Cat5 cables. Braided for noise cancelling and ferrites for the same reason.

After quite a lot of trouble (see another thread) , it´s finally ready to crawl. DIY cab turned out OK. Notice the charming up-side-down faceplate 

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Sounds very nice. Princeton on stereoids. Miss reverb and effects loop though...

I think the original problem must have been that I got solder into one tube soccet. Replaced 3 soccets (got hold of some "good quality" ceramic ones from a friend), and then a few, new problems occured. One soccet was actually broken, so that was changed back to the original.
Also found two wires from the main board to V1, that was partially broken inside the cloth insulation. Replaced these, and now it seems to be fine.
Discovered later tonight that when the amp is cold, I´ve still got a very low scraping sound the forst 30 secs. but after that, it is dead silent. I´ll let it stay this way for now. Bias set at 25 and it sounds sweet!

Must thank Nik for patiently helping with debugging!

I´ll post a few pics in a new thread later tonight.

Thanks!

No prob. - no more 

Tube   Type   Pin1   Pin2   Pin3   Pin4   Pin5   Pin6   Pin7   Pin8   Pin9   
                                 
V1   12AX7   142      1,2         150      1,3      JJ
                                 
V2   12AX7   228      2,2         280      76      Sovtek
                                 
V3   6V6GT   37      393   388   -28         37      
                                 
V4   6V6GT   34       394   388   -28         34      
                                 
V5   GZ34            321      330            
                                 
OT CT   399                              

And life is good.

Getting weirder and weirder.
Voltage readings done over again, now with tremolo switched off.  Readings seem to be OK I think, except for V5 Pin 4 at - 40 (should be +313 or something like that). V3 and V4 pin 8 also are low, at 11 and 13 (should be 27).
Also footswitch makes the tremolo effect really weak (almost inaudible) and when switched off the amp starts popping like a machine gun.

I´ve got Nik trying to help. I´m completely lost.

Some strange readings, and impossible to get a decent reading on V2, pin 1 and 3. Low readings on V3/V4, pin1 & 8.
Could this be a faulty tube (V2?)?



Prinzeton         240V      10/8/10               
                                 
Tube   Type   Pin1   Pin2   Pin3   Pin4   Pin5   Pin6   Pin7   Pin8   Pin9   
                                 
V1   12AX7   145      1,15         165      1,3      JJ
                                 
V2   12AX7   ?       1,6 - 2,6         280      85      Sovtek
                                 
V3   6V6GT   0,2      390   395   39         13      
                                 
V4   6V6GT   0,2       390   395   35         11      
                                 
V5   GZ34            314      332            
                                 
OT CT   408                              

Yes, I´ll post pics if I cannot solve it tonight. Thanks.

Well, it had to happen. After having built both a OTS HRM and a 2550, I thought this would be easy. Not so.
When starting the thing up, the 6V6 tubes are glowing with a pulsing blue light, and noice (scratching) is heard loudly through the speaker. I have checked the layout and all solders, and cannot find anything wrong!

Anyone have any idea where to start looking? I´m handy, but no engineer, so I´m a little lost right now...

 

Indeed it is  . A few hours sleep, and everything seems less complicated 
Thanks anyway.