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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Thu Sep 12, 2019 6:49 pm
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The silver Sprague cap...polarized, if so...which lead is negative?

Thanks,

RB3988




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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Thu Sep 12, 2019 7:27 pm
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Note the crimp around one end of the cap -- orient and install it exactly like the one you'll be removing.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Thu Sep 12, 2019 7:46 pm
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Thanks Arjay...

Capacitor is now a 25uf/25V. First start up, Tremolo took about 6-7 seconds to initialize after engaging the foot switch. I'll turn the amp off...wait until morning (12 hours from now) and test it.
I'll replace that 100K ohm resistor as soon as I get one.

Update: I turned amp on this morning, 12/13 after 12 hours of off time...instant Tremolo after engaging the foot switch!
I'll repost after another 8 hours of amp being off.


RB3988


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Fri Sep 13, 2019 4:35 pm
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RB,

That's encouraging news. I almost missed your update. Let us know how it comes out.


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Fri Sep 13, 2019 6:06 pm
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That's gratifying to hear, Roy!

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Sat Sep 14, 2019 9:29 am
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I turned the amp on, just now...it had been off for 12 hours...hit the foot switch, Tremolo took 45 seconds to initialize, while it was doing so I heard the "motor boating" if the speed control was run up to 9 or 10, after the circuit kicked in, no motor boating at all.

Something else is clearly going on...I can see in the schematic there are numerous other resistors in that Tremolo channel as well as the Tremolo circuitry...one, or more look to be 1M ohm resistors...maybe the problem lies in there. I'll repost as soon as I change out the 100K resistor. Yesterday it engaged immediately after being off for 12 hours, not today.


RB3988


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Sat Sep 14, 2019 6:53 pm
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Sounds like a tech, in the past, tried the blackface "fix the ticking tremolo." The following is from an old RG Keen post. Check the last bullet point and see if it matches what you are seeing in your amp.


" Fixing the "Ticking" in Fender Tremolo circuits."

This is from the great electronics guru R. G. Keen. For an astonishing amount of information about tube amps and guitar effects check out his website, geofex.com.

• Fiberboard contamination: Dust, dirt, and junk can let the LFO signal leak into the audio path. Vacuum the dust and dirt away, and if it still persists, remelt the wax top and bottom with a hair dryer.

• Solder blobs from eyelets touching insulating board: Sometimes excess solder drips out the bottom of an eyelet and can intermittently contact the insulating board, can cause ticking. Remelt the eyelets and examine the board underneath for any blobs dripped down.

• Funny ground on some SF Fenders; On one of the signal tubes, the cathode cap was placed on the tube socket, and wired to a ground lug on the vibrato cancel jack instead of across the resistor on the fiberboard. The vibrato shares this ground line, and can the vibrato current can cause audible ticking in the audio path. Rewire the cap to another ground or relocate it to the board.

• Poor Signal wire layout: signal wires run too close to vibrato leads can pick up the LFO signal. Move them around and see if the ticking goes away.

• Bad repair/replacement foot switch cable: the Fender foot switch cable is not two conductor; it's single conductor shielded, plus single conductor. The reverb wire is shielded, vibrato wire is not. This keeps vibrato out of reverb. If you retrofit with two conductor shielded, you get vibrato ticking onto reverb audio.

• Sharp tick in vibrato oscillator: On neon/LDR Fenders, on the neon bulb side of the module there is a 10M to one side of bulb, 100K to the bulb; from the 10M straight across the board is the gnd point of the LDR. Put a 0.02 cap from 10M/bulb to the ground point; this works by filtering the output of the oscillator.


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Sat Sep 14, 2019 10:38 pm
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BMW2002Ti,

I think your opening comment sums it up..."Sounds like a tech...". I bought this amp used back around 2004...give or take a year. It was damaged in shipping and I had a tech here in Souther California bring it back to life.
I do not recall if he mentioned anything about the Tremolo Channel at all...but when he got the amp, who really knows who else had tinkered with it prior?

I think I will move forward, replace that one 100K ohm resistor and if that does not fix it, I will likely just keep it and live with the idiosyncrasy. I like the amp...I just wanted it to operate like "new"...which it is not.

Thanks again,

RoyB3988


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Sun Sep 15, 2019 11:18 pm
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Team, from one of my posts back in August:
"I cannot say to a certainty if those items have been checked. The last time a tech had the amp was in early 2017...due to fuses blowing. While I waited and watched he put in a new fuse, picked up the chassis and twisted it while he watched his scope. On the second fuse he turned the chassis upside down and shook it...a small piece of what he called "old solder" fell out. On the 3rd fuse he replaced the V2 12AX7 with a new Tung-Sol and we played the amp for 10 minutes...but at that time the Tremolo was not a problem. He charged me $20 including the tube and fuse."

When the tech picked up the chassis and twisted it, might he have broken a connection/component somewhere in the chassis? As best I can recall, the intermittent problem with the Tremolo began shortly after that visit...as time passed it became more frequent.

Since the Tremolo does work...albeit with a glitch or two...It might be time to accept the probability the amp "is what it is" and simply play it...as it is.

Thanks,

RB3988


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Mon Sep 16, 2019 9:07 am
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Did you ever check to see if the intensity control is the problem? Every symptom you describe indicates that the LFO engages instantly when you activate the tremolo with the footswitch, and that the neon lamp is firing, as it is the source of the ticking sound. The LDR has been replaced when you replaced the LDR/neon lamp assembly earlier. The only thing between the LDR and the audio circuits is the tremolo intensity control. If the wiper of the control is dirty or the carbon track is worn, the tremolo will be intermittent.

Dave


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Mon Sep 16, 2019 11:01 am
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dcgillespie...

I will check it sometime today...I also noticed that when I turned the amp on this morning...it had been off since 11PM last night, the Tremolo went almost 60 seconds after I hit the foot switch and had not engaged...as soon as I touched Tube V3 the Tremolo kicked in. The hassle here is waiting the several hours it takes for the amp to be off long enough for the Tremolo to NOT work properly after the amp is turned on. I will check that tube and tube socket as well. Again, when I hit the foot switch I could faintly hear the pulsing of the Tremolo...then when I touched the tube it came on as it should.

Thanks,

RB3988


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Mon Sep 16, 2019 12:34 pm
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Don't ya just hate intermittents? Dirty or bad tube socket is always a possibility with weird goings on.

Dave


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Mon Sep 16, 2019 8:14 pm
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Dcgillespie...yes, intermittents can make things get real crazy real fast. As I think back, I don't think I have ever had good luck with tubes bought on the "Bay...". Maybe I should invest some cash in quality tubes...a complete set.

I ordered some resistors and will report back after I change the infamous "100K ohm" that is in the Tremolo circuitry near the opto coupler.

RB3988


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Mon Sep 16, 2019 9:43 pm
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I use wooden chopsticks to prod around the circuit, for bad solder points and damaged resistors. Cold spray to try and isolate other cold solder or weak connections.

https://www.amazon.com/MG-Chemicals-Sup ... way&sr=8-5


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Post subject: Re: Fender 1967 DUAL (in block letters) Showman
Posted: Tue Sep 17, 2019 9:56 am
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When you folks buy tubes for your amps...do you trust tubes from sellers on $bay? Not sure if I can mention that site by name here.
All 3 12AX7 tubes in the amp are Tung Sol "reissue" tubes I bought last year on the "bay". They have never been used until yesterday and depending on which tube is in which V slot...I get motor boating, even if one of them was in V1 ! I finally found 3 that give me no noises and this morning the amp fired up, I hit the foot switch after proper warm up and the Tremolo engaged immediately. This happened a few days ago but I was getting the motor boating noise so I started substituting tubes around.
And the beat goes on...

RB3988


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