Another great video, Stuart! The reverb circuit in the Vibro-King is a built-in version of the original Fender stand-alone reverb tank. It was a selling feature of the amps when they were introduced. The only time I heard ticking that bad in a Fender tremolo circuit I changed the "roach" because nothing else worked and I had a spare on hand. It fixed the problem, but I didn't understand why - thanks to Jerry Ogle for suggesting the bulb may be too close to the photo resistor. Thanks for making these videos. They are a wealth of practical trouble shooting know how.
I found this issue in with the same tone stack (Commonly in Marshalls), exactly the same symptoms (this "frying bacon" sound). The C7-150pf ceramic (or mica) capacitor was the culprit in all cases. This capacitor was not blocking the DC properly which means a leaky capacitor sending DC current to inverter valve and power valves. This is not an easy issue to find due in the most cases this capacitor do not reacts to tapping it. Great video!
I'm 10 mins into your video and I wish I could remind you that some Fender amps have the treble pot passing the entire signal to ground. You had one doing that in one of your videos a while back. Now to get back to the video and see how you sort this one out. Btw I appreciate you making these i have learned so much watching you fix amps.The good people of Berkshire are lucky to have you. Keep up the good work.
Hey Stuart..Great video, love the walk thru and your methods of fault finding. Bit of a pest that ticking noise..! Good fix, look forward to your next excursion...Ed.uk..😀
You don't see too many modern Vibro King amps in the UK. Very expensive and the weight ! ! .. I worked on an older one a few years back with the ticking tremolo . The 10nF cap from the 10 Meg resistor to ground didn't get rid of the tick but reduced the volume of it. I fiddled around with the roach and pulled back the heatshrink tubing a little and it solved the issue.. I might have just got lucky or disturbed something else on the board. Great video again Stuart.
@@stuartukguitarampguy5830 A very good point, well made.. Don't know.. It could have been I disturbed something in the vicinity or just got lucky. I only play at this stuff and am in no way qualified ..That's why I watch your videos, ha-ha..
I currently own one of these and life the tone of this amp! Mine has the ticking and noise issue this one has. I pulled the bulb slightly out of the sheath on the roach and the problem was greatly reduced. I may try replacing it later. I will be doing some investigation into the noise from the time circuit but feel it's the same problem...Id like to just recap the amp as well. Thank you for this video!
Ok pulling the bulb out slightly may have simply reduced the intensity of the vibrato and hence reduced the ticking also. Most times I find I can cure it by lead dress. USe a chopstick or something to carefully move wires around to see if you can get a reduction.
Well found. That ticking is something else, a design flaw (if none of the usual fixes work)? Are 115 volt amps common in the UK (imports?) as I can't imagine people lugging step-down transformers to gigs, but then, when compared with the weight of the amp!
I kind of like that cabinet effect. Really enjoyed this fix Stuart, part fix anyway. A grip as you said, never heard that expression. Is that related to the same grips you see on the credits of movies etc.
Hi Otto. I don;t know where it came from, I picked it up in my days at Television Centre (BBC) in the 1970s. We always used to say "That's a grip!" if we fixed a problem.
I have a vibro king. The reverb has lost some of it's strength. I.e. I have to turn the reverb up more than I used to. I change the reverb tube, not much difference. any idea why ?
@@stuartukguitarampguy5830 I did the freon spray but nothing helped. The coupling cap's seem to be okay. The bacon frying noise is intermittent - I suspect a bad solder joint somewhere.
@@bryanbailey6963 Hi Bryan. I had one just recently with exactly this issue. Took me 2 hours and freezer spray didn;t make the slightest difference in the noise. Ended up swapping coomponents in the section one by one. Turned out to be a 3K resistor! Very surprised that freezer didn;t affect it at all.
@@stuartukguitarampguy5830 Stuart: Can you say which 3K resistor you replaced on the schematic? I cleaned the shunt contacts on the FX and F/S jacks and the noise went away, but I am not confident that was the fix. It seems more coincidental. I looked at the schematic and the closest I see is a 2.7K on pin 8 of V6. (The one I am fixing has the 6V6 for the reverb.)
@@stuartukguitarampguy5830 Stuart every time the neon ignites the gas in the bulb there’s a high voltage arc that radiates a noise signal into the photocell and intensity control circuitry. The output of the intensity control goes to the grid of the inverter tube then to the output. In your video when you adjusted the intensity you turned off the ticking. Like and old spark gap transmitter.
@@jerryogle8798 Thanks Jerry that's really helpful. Hmm, I wonder what the cure is though as the neon is always tight up against the photocell and indeed held there by shrink sleeving!
@@stuartukguitarampguy5830 think I would just try replacing the photocell . Over time it could just be breaking down. Stuart look forward to your videos learn something new everyday. I’m 71 retired and still learning. Keep up the good work‼️Thanks
When I saw how the amp reacts to treble pot I was pretty sure it's this cap's fault. I see volume pot is not after the tone stack, but between the preamp stages so it has no influence on noise. Replacing mica cap with a ceramic one? Never did that, would probably never, but on the other hand ceramics are pretty indestructible and at such small values all the drawbacks of ceramics are neglectable. Those tone stack component values are something I've never seen before (I expected it to be Marshall style from cathode follower), especially 100k resistor after it all. Can't stop thinking why would they make a vibrato lamp driver with tubes instead of transistors - no sound passes through ... And use a vactrol instead of neon light assembly ...
I can't stop laughing what the hack is wrong. Facesplitter out there would be any sound ratling. That noise is formiliar to socket noise. I use high grade mkp caps. You found the bad cap. If the voltage DC leakage was higher it could damage more. Well fixed that. 👍
