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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Sun Jun 24, 2018 12:29 am
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Thank you, Arjay! It is great that you (as an actual back-in-the-day user of one of the Fender SS amps) share your experiences.

I too believe that the SS PA-system had the same output stage configuration as the high-power instrument amp of the same series. What you write confirms that the amps worked quite well when used the way they were intended to by design (i.e. in the reasonably linear range) - even when pushed. Your input also indicates that we shouldn't have been that worried when we investigated and recorded our SS TR, and could have been more confident. But then, it is an old amp – so: better safe than sorry :-).

Do you remember whether your PA amp had a thermal fuse (that would have required replacing in case it blew) in the back for short-circuit protection, or whether it had the circuit breaker with a reset-button?

Regards and a good Sunday,

Tilmann


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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Sun Jun 24, 2018 2:25 am
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The rear panel featured a resettable thermocouple (red push button) as well as a standard fuse post and a three-position polarity switch. I'm pretty sure the guitar amps used the same configuration.

Arjay

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Sun Jun 24, 2018 5:03 am
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So yours was the later version with the resettable circuit breaker - as you can see in the pix we took (Fig. 4 & 5 in https://gitec-forum.de/wp/wp-content/uploads/fender_ss_twin_reverb_pt_1.pdf), our SS TR is an earlier version that still had the regular fuse in the output line. The switch to the circuit breaker is off course a real improvement because the user does not have to carry extra fuses.

Did the circuit breaker in your amp ever become active (in the sense that it switched off the output)?

Cheers,
T.


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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Sun Jun 24, 2018 8:32 am
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I suspect that only the U.S. models got the circuit breaker. The export models got the voltage selector with incorporated fuse so the fuse could be changed to the correct rating depending on the voltage selected.

Just my opinion, of course. I have no experience with these amps, have never seen one "in the flesh" so to speak, just pictures.

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Sun Jun 24, 2018 9:43 am
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OrangeJBL wrote:
So yours was the later version with the resettable circuit breaker - as you can see in the pix we took (Fig. 4 & 5 in https://gitec-forum.de/wp/wp-content/uploads/fender_ss_twin_reverb_pt_1.pdf), our SS TR is an earlier version that still had the regular fuse in the output line. The switch to the circuit breaker is off course a real improvement because the user does not have to carry extra fuses.

Did the circuit breaker in your amp ever become active (in the sense that it switched off the output)?

Cheers,
T.


No......mine was one of the very first PA 4100's to be produced (as I stated, it was purchased new in 1967). It had both thermal-overload protection AND a conventional line fuse.

Your specimen is an export model, with some key differences to the rear panel layout, just as "vinyl" (above) has opined.

Arjay

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Sun Jun 24, 2018 10:32 am
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Thanks so much for your support, both dear Arjay and dear vinyl - I very much appreciate it!
About the circuit breaker: please note that it has nothing to do with the line-voltage that is different in Europe and the US. This is about the speaker output protection which in both the domestic and the export versions would likely to be the same because the output power is the same irrespective of the line voltage. I would find it surprising if Fender would arrange for a different speaker output protection with the power stage being identical otherwise. But then ... who knows :wink:
Anyway, this is not really a very important question - I just find it interesting that Fender were in fact aware that the missing electronic short-circuit-protection was a potential issue and - possibly as a kind of afterthought - tried a more "hard-ware-based" precaution.
Again, many thanks - and a good start into the week for you,
Tilmann


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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Tue Jun 26, 2018 5:50 pm
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Tilmann,
I hope this week is going well for you also.
I very much enjoyed visiting Műnchen years ago. I particularly liked the Duetches Museum, especially the guy in the Farraday cage.
I don't have access to a 1969 Fender Catalog, but I suspect the output protection you describe never came to be. By 1970, the "zodiac line" showed up, but they were nothing more than the same circuit boards mounted in a different chassis.

Here's a pic from someone's blog showing the inside of a "Libra" amp:
Image
Notice thecircuit board is identical to your amp. It even has the same part numbers. These amps had a circuit breaker on the electrical input, and a 6 amp fuse for the output mounted on the bottom of the chassis.

Fender catalogs are not the best source of accurate information. as an example, I would direct you to the '68 catalog which states the bassman is the equivalent of a 12 tube amp because of the twin triode tubes used. If you add up the tubes, and the fact that one of the 7025 tubes doesn't use both halves, the most you can come up with is 9 tubes.

I know you said it's not an important question, but it did more to damage Fender's reputation than the fact that they made a solid state amp that didn't sound good they made one that was unreliable, and they then took the same unreliable amp and stuck it in a different chassis and still sold it.

In the 68 catalog, they say "semi-module" construction makes for simplified repair. Translated from marketing speak means you replace the whole circuit board, which I suspect may have happened to yours, given the 69 dates marked on them. It's hard to tell but the power transformer looks like it might have 66 date.

Image
Image

Notice the similarity to your power amp board in this Libra amp, and the fine example of Fender CBS "quality".
Image

Drill a hole, solder in a jumper.

All of that said, there's nothing wrong with a solid state amp if you're looking for a "clean" sound.

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Tue Jun 26, 2018 7:54 pm
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vinyl wrote:
All of that said, there's nothing wrong with a solid state amp if you're looking for a "clean" sound.

So long as it doesn't blow up and/or catch fire.

:mrgreen:
Fender's first-gen S/S amps were all equipped with wave-soldered circuit boards and this technology caused problems because the automated machines were never calibrated correctly nor cleaned as often as they should have been. The lion's share of these amp's catastrophic failures were directly attributable to this. The follow-on "Zodiac" series of amps were marginally better only due to the fact that the notorious (and often spectacular) malfunctions were largely solved as Fender's assembly techs became more familiar with the wave-solder technology. But Fender's second effort at transistorized platforms failed just as miserably as the first because the designs still had the same resonance, tone, and timbre as a stainless-steel GI-issue canteen cup.

Arjay

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Thu Jun 28, 2018 11:58 am
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Long time ago I had a '60's Baldwin solid state Supersound 1x12" amp that sounded pretty sweet when overdriven - don't know why or how... or maybe it sounded awful and i just don't remember right!


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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Fri Jun 29, 2018 3:02 pm
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Some great discussion and info-exchange here! MANY THANKS in particular to Vinyl for the Info on the Libra amp! I had not seen such detail on the "Zodiac"-Amps before, and while I have read somewhere that Fender continued to use design features of the first solid-state amps, I am surprised that in fact the very same circuitry AND even the same boards apparently have been used at least in some sections. I very much appreciate the input regarding possible repairs in the amp the we investigated here - you point out some aspects that I did not consider at all before, and I am very happy to be helped to have a wider-angle view.

I fully concur that the Fender catalogs (while they do make for amusing reading :-) ) are quite poor sources for accurate info - that is why the exchange on a forum such as this one is so helpful if the actual amp is not at hand.

I also very much concur that it must habe been the reliability issue that did more damage to the Fender name than anything else. The sound of the amp is in the "ear of the beholder" (and I do maintain that the SS TR does not sound bad at all for what it was), but reliability is measurable and very objective make-or-break issue (as Arjay so eloquently points out in his posts via B.Z.). When I wrote "not so important" I was referring the the question of which version had which output stage protection. Reliability and serviceability are of course SUPER-important issues!

Thanks to all for helping me get a fuller picture of what was going on at Fender when the first SS amps and then the Zodiacs came out.

Have a great weekend,

Tilmann

P.S.: special note to vinyl: I am glad you had a nice experience in Munich and even got to visit the Deutsches Museum! Indeed the high-voltage show is always a winner (I do not know how many employees were used-up over the years in that Faraday-ball-cage;-)). There are some serious extensions being added to the Museum (even in various parts of the city), and they also have some more cool airplanes on display now - although I still think it is nothing compared to what the Smithsonian offers. In any case, if you decide to re-visit sometime, drop me a line so I can treat you to a beer!


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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Fri Jun 29, 2018 4:26 pm
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OrangeJBL wrote:
...and they also have some more cool airplanes on display now - although I still think it is nothing compared to what the Smithsonian offers.


What types of aircraft?

Arjay

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Fri Jun 29, 2018 5:32 pm
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OrangeJBL wrote:
I still think it is nothing compared to what the Smithsonian offers. In any case, if you decide to re-visit sometime, drop me a line so I can treat you to a beer!
The Smithsonian is a great museum because of the diversity of one-of-a-kind historical craft like the Bell X-1, Apollo 11, Apollo-Soyuz backup craft, etc....

But for someone who is simply an aviation geek, no museum on the planet surpasses Wright-Patterson in Ohio. Number 2 is the Pima museum in Tucson AZ.
Make the Pima trip a 3-4 day event. It really takes two days to go through the museum, then you can sign up for the AMARG (boneyard) tour, and finally, spend a half say south at the Titan Missile Museum and take the full tour when you climb down the silo and stand under the engines of a real ICBM.

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Fri Jun 29, 2018 5:53 pm
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Redfarfisa wrote:
Long time ago I had a '60's Baldwin solid state Supersound 1x12" amp that sounded pretty sweet when overdriven - don't know why or how... or maybe it sounded awful and i just don't remember right!


Kustom had some pretty good solid state amps, or at least Bob Kuban and the In Men managed to make them sound good. Gayle McCormick would show up some times before she joined Smith. Yeah, I grew up in St. Louis.

Quote:
Number 2 is the Pima museum in Tucson AZ.
Make the Pima trip a 3-4 day event. It really takes two days to go through the museum, then you can sign up for the AMARG (boneyard) tour, and finally, spend a half say south at the Titan Missile Museum and take the full tour when you climb down the silo and stand under the engines of a real ICBM.


+1.

I sort of made a vow after returning that I would never make a "+1" post, but I have to make an exception in this case. The Pima museum in Tucson is that exceptional.

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Fri Jun 29, 2018 6:33 pm
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vinyl wrote:
Yeah, I grew up in St. Louis.


Just down the road (I-70) from Chanute, Kansas where the Kustom plant was located.

Arjay

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Post subject: Re: Vintage Fender Solid State amps-where did they go?
Posted: Mon Jul 02, 2018 12:14 am
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While we are staying off-topic now considerably, I need state that I was privileged enough to be able to visit both the museums in OH and AZ. Absolutely amazing! Just thinking of the XB-70 as it towered above and spanned across the hall still sends chills down my back!

... back ... now we better go back to amps and discuss planes elsewhere .... :wink:

Have a good day!


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