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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Nov 04, 2013 8:30 am
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Haha yeah, I used to do "micro drilling" for fiber optic parts where the holes were three thousandths of an inch in diameter! It was amazing stuff. Before that I made gears for automobile transmissions for Getrag Gears and before that, I worked in a custom jobbing shop on transmissions for Navy Ships were some of the gears were twenty seven feet in diameter and hoisted into position with two overhead 50 ton cranes. Today, it's all CNC stuff. Doesn't pay what it used to and not as much fun. All these companies moved to other locations for cheap labor. I got out and went into business for myself. It was fun while it lasted.

"Only" a Machinist? :lol:

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Nov 04, 2013 1:25 pm
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OK, very funny, but you guys missed my point, which was that he did very well with electronics, amps and guitars, for someone having a background as a machinist. "Only a machinist", as in no electronics background, not as a knock against machinists. I am one that fixed those machines when they didn't work, because the machinists couldn't do the repairs, especially the electronics part. Machinists are OK, heck, some of my best friends are machinists. :lol:

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Nov 04, 2013 3:26 pm
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shimmilou wrote:
OK, very funny, but you guys missed my point, which was that he did very well with electronics, amps and guitars, for someone having a background as a machinist. "Only a machinist", as in no electronics background, not as a knock against machinists. I am one that fixed those machines when they didn't work, because the machinists couldn't do the repairs, especially the electronics part. Machinists are OK, heck, some of my best friends are machinists. :lol:


I fixed my CNC turning centers both electronically and mechanically. I did trouble shooting, replaced boards and joysticks when my jackhole daytime operator broke it off by dropping blank parts on it, repaired and trued the machine after someone (the same guy lol) would crash and index the turret into the chuck. Replace gauges and hydraulic lines when needed and did much of the required maintenance. This was way back when it was new technology and we used program tapes on giant GE consoles. :lol: Not all Machinists are only Machinists. We are Mechanics and Electricians/Electronic Technicians too. In the one company I worked for it was common. I'm not saying we could do everything, and fix anything, but we were pretty smart guys. :lol:

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Last edited by 63supro on Mon Mar 10, 2014 6:02 am, edited 1 time in total.

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Nov 04, 2013 4:09 pm
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shimmilou wrote:
OK, very funny, but you guys missed my point, which was that he did very well with electronics, amps and guitars, for someone having a background as a machinist. "Only a machinist", as in no electronics background, not as a knock against machinists. I am one that fixed those machines when they didn't work, because the machinists couldn't do the repairs, especially the electronics part. Machinists are OK, heck, some of my best friends are machinists. :lol:


I didn't intend to come off snarky, shimmilou. If it sounded that way, lo siento.

8)

Arjay

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Nov 04, 2013 5:37 pm
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Retroverbial wrote:
shimmilou wrote:
OK, very funny, but you guys missed my point, which was that he did very well with electronics, amps and guitars, for someone having a background as a machinist. "Only a machinist", as in no electronics background, not as a knock against machinists. I am one that fixed those machines when they didn't work, because the machinists couldn't do the repairs, especially the electronics part. Machinists are OK, heck, some of my best friends are machinists. :lol:


I didn't intend to come off snarky, shimmilou. If it sounded that way, lo siento.

8)

Arjay



+1 Me either. :wink:

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Tue Nov 05, 2013 7:53 am
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Thanks guys. I realize that I might do a better job of choosing my words in the future, as I didn't mean anything negative, but meant it as a compliment.


63supro wrote:
...This was way back when it was new technology and we used program tapes on giant GE consoles...


That does bring back memories of the old paper punch tapes on CNC machines. Kudos for being able to work on those machines. 8) We've come a long way since then. :!:

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Tue Nov 05, 2013 9:39 am
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Back on topic, I was able to score a schematic for my 68CDR by contacting Fender Consumer Relations-took a few days for him to get it to me as they are so new but they are available.
I'd post it here(PDF file)but I can't figure out how! :oops:


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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Tue Nov 05, 2013 2:24 pm
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Hi t-luxe,

Check your PM inbox.

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Wed Nov 06, 2013 10:15 am
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shimmilou wrote:
Thanks guys. I realize that I might do a better job of choosing my words in the future, as I didn't mean anything negative, but meant it as a compliment.


63supro wrote:
...This was way back when it was new technology and we used program tapes on giant GE consoles...


That does bring back memories of the old paper punch tapes on CNC machines. Kudos for being able to work on those machines. 8) We've come a long way since then. :!:



Oh yeah Lou, I think I still have a couple in my toolbox. I did work with some nice Hitachi CNC turning centers though. :lol:

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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Sun Mar 09, 2014 5:12 pm
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t-luxe wrote:
A gut shot of my '68 CDR.

NFB resistor is 1.5k, instead of thr DRRI's 820.


Thanks for posting this shot. Where is the negative feedback resistor? If i put a resistor in parallel (approx 1.8kohm) with it, won't that put it at the DRRI specs? I've been reading that the NFB tweak could be causing the massive amount of idle noise, which is a real issue on an otherwise amazing sounding amp. Thoughts?

Also, does anyone know the value of the NFB resistor on the silverface and blackface amps (vintage)?


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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Mar 10, 2014 4:04 am
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polishbroadcast wrote:
t-luxe wrote:
A gut shot of my '68 CDR.

NFB resistor is 1.5k, instead of thr DRRI's 820.


Thanks for posting this shot. Where is the negative feedback resistor? If i put a resistor in parallel (approx 1.8kohm) with it, won't that put it at the DRRI specs? I've been reading that the NFB tweak could be causing the massive amount of idle noise, which is a real issue on an otherwise amazing sounding amp. Thoughts?

Also, does anyone know the value of the NFB resistor on the silverface and blackface amps (vintage)?


Read the part that you quoted above. t-luxe already answered that. The increased value of the NFB resistor decreases the negative feedback.

Edit: sorry I forgot to circle the resistor, but it is the only 820 showing up. /Edit

Both of these are blackface, but the Deluxe Reverb didn't change much over the years until CBS started screwing with master volumes in the mid 70's.

AB763 circuit:
Image

AB868 circuit:
Image

Looks like 820 ohms in both cases

Art


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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Mar 10, 2014 8:29 am
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Art1 wrote:
Read the part that you quoted above. t-luxe already answered that. The increased value of the NFB resistor decreases the negative feedback.


Thanks for the location answer Art.

Which "that" are you referring to? I was wondering 3 things (of which you already answered 1) but I'll try to be more clear:
  • Will putting a 1.8k resistor in parallel with the existing NFB resistor put the amp at RI / vintage values. This should give the 820 ohms which increases NFB. Right? (just verifying I'm thinking about the electronic theory correctly)
  • Will adding this resistor in parallel reduce the noise to at least DRRI levels or are there other noise contributors?
  • What is the RI & vintage NFB resistor value and location? (answered. thanks!)


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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Mar 10, 2014 8:59 am
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Inverse summation, for resistors in parallel. (1/R,sum = 1/R,1 + 1/R,2 ... +1/R,n)

For 820-ohms plus 1800-ohms, I get a resultant 563-ohms. Less resistance = greater GNFB voltage. Or "more" feedback. Now, just how this effects the tone is not quite that simple. This is somewhat system dependent. Best to do empirical testing. Try it, and make notes of the change (if any) to the tone.

The result maybe a more sterile sound, heftier bass, or no effect at all. Be careful with modifying these amps with circuit boards. Try to keep the tracings and pads intact.

Good luck!


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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Mar 10, 2014 9:03 am
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polishbroadcast wrote:
Thanks for the location answer Art.

Which "that" are you referring to? I was wondering 3 things (of which you already answered 1) but I'll try to be more clear:
  • Will putting a 1.8k resistor in parallel with the existing NFB resistor put the amp at RI / vintage values. This should give the 820 ohms which increases NFB. Right? (just verifying I'm thinking about the electronic theory correctly)
  • Will adding this resistor in parallel reduce the noise to at least DRRI levels or are there other noise contributors?
  • What is the RI & vintage NFB resistor value and location? (answered. thanks!)


My 68 Custom schematic is hard to read but it "looks" like a 1.8k or 1.9k. (I would have to open mine up to verify that value.) So two 1.8k would give you 900 ohms. Much better to replace with an 820 ohm, but why? You will be affecting the "Vintage" as well as the "custom" channel. Unpredictable results on the tone. You will also be killing your warranty.

I believe there may be other noise contributors, wire placement and so forth. Two 68 Customs assembled by two different workers can produce differing levels of noise due to that slight difference in wire routing, grounding wires (placement, tightening of screws, etc...) length of wires, quality of solder joints, and so on. Tubes (valves) used can have an impact on noise as can the most overlooked component, the instrument cable. Even in an amp that uses a PC board, there are human factors that can affect the quality of audio output, or the perceived quality of output.


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Post subject: Re: '68 Deluxe Reverb problems...
Posted: Mon Mar 10, 2014 9:11 am
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Art1 wrote:
Both of these are blackface, but the Deluxe Reverb didn't change much over the years until CBS started screwing with master volumes in the mid 70's.


It's also 820 ohms in the pull-boost versions of the late '70s.

Arjay

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