| Author |
 Topic  |
|
Laurie
Double Platinum Member
Canada
4854 Posts |
 Posted - 03/11/2010 : 14:24:40
|
This is a well understood problem with Fenders - a "ticking" sound when you crank the depth of the vibrato up.
There is a HEAP of discussion in the www about how to fix it, but I was wondering if anyone hear had actually run into this and had first-hand experience fixing it? My vibrolux has just started doing it (after I had my hands in it on the weekend undoing a couple of mods - unrelated to the vibrato). |
|
|
zerksies
Double Platinum Member
USA
3406 Posts |
Posted - 03/11/2010 : 14:29:38
|
| Replace the 12At7's both of them. I had that new tube does it all |
 |
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/11/2010 : 14:32:38
|
quote:
Originally posted by zerksies
Replace the 12At7's both of them. I had that new tube does it all
Tried that. And the output tubes. No change.
The research suggests I've disturbed the wiring loom when I had it apart... the "lead dress". |
|
|
|
Witloofboer
Gold Member
Belgium
513 Posts |
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/11/2010 : 22:59:05
|
Thanks! My challenge is that the "CVR" is one of the very few Fender amps that doesn't use an opto-coupler for the vibe..... |
|
|
|
FRANZONI
Double Platinum Member
Ireland
3543 Posts |
Posted - 03/12/2010 : 02:28:18
|
I get the ticking noise sometimes with my dynacord leslie unit but turning it off for a few seconds and back on seems to sort it...i have two amps(non fender although Leo did have a hand in Musicman) AFAIK i think my Selmers tremolo/vibrato works on part of the circuit altering the bias to a tube to create the effect like the early vox amps...the Musicman as it's partly transistorised so i'm not sure how the tremolo effect is created but as it's early 70's and built by mostly EX Fender employees maybe they sorted that problem in the design....
When you say a "heap of discussion" and are looking for 1st hand experience i take it your not entirely convinced by the answers people have posted to this problem...?.....to be honest Laurie a few of us dabble but there aren't many amp gurus here..us guys look to you and Dr Bob etc... for that sort of advice...
|
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/12/2010 : 02:37:17
|
quote:
Originally posted by FRANZONI
When you say a "heap of discussion" and are looking for 1st hand experience i take it your not entirely convinced by the answers people have posted to this problem...?.....to be honest Laurie a few of us dabble but there aren't many amp gurus here..us guys look to you and Dr Bob etc... for that sort of advice...
Yeah, I'd really like to hear from someone who has fixed it. The discussion talks to optocouplers (which i dont have) or lead dress, which seems too "mushy". But, I'll admit I haven't opened it up to try the lead-dress thing, so that's the next step.
Thank you to everyone for the thoughts  |
|
|
|
hateandwar
Gold Member
Australia
524 Posts |
Posted - 03/12/2010 : 09:11:34
|
Unfortunately i cant give you any advice, but with my new amp (eminar) there is a bit of a ticking sound when your not playing. But its not enough to reaaally annoy me.
Mainly because when its on, it just sounds beautiful. I tested it with the TR-2, and i gotta say the TR-2 comes extremley close. But not close enough for me. (sorry boss!) |
Edited by - hateandwar on 03/12/2010 09:12:14 |
|
|
|
Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/12/2010 : 19:04:52
|
Hi Laurie
I have PM'ed you about this.
I need to know which revision of the Vibrolux Chassis you have.
I'm gong to put even money on it being lead dress, or damp on the eyelet board.
Non of my current Fenders Have Vib. & as you well know from my PM's
I miss that very much.
And that's why I've been on a quest, to find a pedal that as close as possible, approximates the Vib. on a Classic Fender Tube amp.
Yes it's been a long search.
But I belive you have found a Danelectro pedal that's close?
Regards Dr. Bob  |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/12/2010 : 19:18:59
|
quote:
Originally posted by Dr. Bob
Hi Laurie
I have PM'ed you about this.
I need to know which revision of the Vibrolux Chassis you have.
I'm gong to put even money on it being lead dress, or damp on the eyelet board.
Non of my current Fenders Have Vib. & as you well know from my PM's
I miss that very much.
And that's why I've been on a quest, to find a pedal that as close as possible, approximates the Vib. on a Classic Fender Tube amp.
Yes it's been a long search.
But I belive you have found a Danelectro pedal that's close?
Regards Dr. Bob
I wish it was an eyelet board. It is, in fact, a "CVR" - with a PCB. There is only one version that I'm aware of.
The Cool Cat tremolo is ... cool. "Good enough", especially for the price, would be my assessment.
I'll pull it apart on the weekend and see if "adjusting its dress" fixes it |
|
|
|
ranjam
Bronze Member
Canada
82 Posts |
Posted - 03/13/2010 : 03:40:41
|
This is just a SWAG (sweeping wild-ass guess), so consider the source. This has the bias-modulation tremolo, where the LFO adds/subtracts from the DC bias voltage. Maybe the bias is set to a weird value that the LFO sends the output tubes into cutoff, and that is the 'tick' you hear. Just for sh*ts and giggles, try a few different bias voltages. Maybe just a few volts + from where it is now? Check the idle current, and maybe that number sends up a red flag or two. Try different output tubes.
Or maybe I'm mixing my meds again.  |
|
|
|
Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/13/2010 : 07:56:59
|
Hi ranjam
Clever & Funny - you always have interesting posts.
Just for your interest, worldly education, & reading pleasure.
in Oz "Meds" are one of the names/terms for Ladies Sanitary Tampons...
Same word two completely Different meanings. 
I'll bet that now, you can't use that word again without laughing quietly to yourself, or completely not at all anymore.
Thanks for cheering me & the other Aussie's up a bit today...
Hey Laurie I'm sorry I hijacked your thread for a bit.
Regards Dr. Bob
|
Edited by - Dr. Bob on 03/13/2010 07:58:12 |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/14/2010 : 19:54:26
|
I'd done the "moyer mods" on the amp as described here:
http://www.vintage-vibe.net/Documents/CVR_to_VV.txt
http://www.bossarea.com/forum/topic.asp?TOPIC_ID=5153
Then I'd backed some of the mods out - specifically I put reverb back to factory spec (on both channels) and put the Jensen speakers back.
I did, however, leave the negative-feed-back loop. And that's what was making the ticking... for some reason, there is an interaction between the NFB loop and the vibe with the reverb going to both normal and bright channels. I put a 1k resistor in series with the feedback signal to lower it a bit and presto the problem is gone.
Swapped to a pair of JJ 6L6 tubes along the way which are much closer to being matched (the old no-label ones in the amp were running about 10mA apart in bias).
So... why did I back the mods out?
1) I wanted reverb on the "normal" channel - it was bugging me that it was only on the "bright" channel. Yes, there is more hisssssss if you have it on both channels, but its acceptable.
2) After they were fully broken in, the Eminence speakers I'd put in went a bit "dark" for a blackface fender. Nice for classic rock, but I have the marshalls for that. I put the jensen P10R's back in and it brightened it back up and gave it the "quack" back.
Interestingly, the amp was owned (and rarely used) by a harmonica player before me, so the P10R's have never really had a guitar signal through them. Talking to the Jensen rep here it became apparent that maybe the P10R's aren't fully broken in (for guitar), and it does sound like that's the case. They are mellowing already.
|
|
|
|
ranjam
Bronze Member
Canada
82 Posts |
Posted - 03/15/2010 : 03:05:14
|
Weird. Increasing the resistor value is moving towards less and less feedback, and less headroom. Sometimes the phasing is 'wrong', where the feedback is in phase rather than out of phase, so the feedback is regenerative as opposed to degenerative. I've swapped Plate leads, and that fixed the problem without having to increase the feedback resistance.
If you want to break in those speakers faster, try http://www.unclespot.com/speakerbreakin.html. I've done it with a Variac, and it works. |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/15/2010 : 03:34:06
|
quote:
Originally posted by ranjam
Weird. Increasing the resistor value is moving towards less and less feedback, and less headroom. Sometimes the phasing is 'wrong', where the feedback is in phase rather than out of phase, so the feedback is regenerative as opposed to degenerative. I've swapped Plate leads, and that fixed the problem without having to increase the feedback resistance.
If you want to break in those speakers faster, try http://www.unclespot.com/speakerbreakin.html. I've done it with a Variac, and it works.
Thanks! Tell me more about the plate leads...? |
|
|
|
ranjam
Bronze Member
Canada
82 Posts |
Posted - 03/16/2010 : 02:44:38
|
Well, the feedback has to be 180 degrees out of phase with where it is coupled to do its job. Go through the stages right from the input; after one stage we'll say -180, after a 2nd stage, it's back to being in phase or '0'. Add a 3rd stage, and it's -180 again. Now the phase inverter (in phase or '0'), an output tube (-180), and the transformer (in phase or '0'). If the feedback voltage is fed back to a stage that the signal is in phase with the original guitar signal, they add up instead of subtracting, so the signal increases. Now it goes back through the phase inverter, the output tube, the transformer, and sends a signal back to the stage where it is in phase, and adds again. Now you have a runaway condition, and it will oscillate. If you ever change an output transformer, and you turn the amplifier on to get a deafening howl, you reverse the Plate leads. Usually on a Fender they are brown and blue. Put the brown lead where the blue lead was, and vice versa.
If I knew anything about op-amps, I'd compare it to the + and - inputs. |
|
|
|
Topic |
|
Fender blackface reissue vibrato "ticking"
