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Tele-Dave · January 29th, 2009, 02:01 AM

On my $200 pawn shop find HRDLx i noticed a strange wiring addition the previous owner must have installed. If anyone has a schem and parts layout, please follow along help me decipher this.

There is a wire from bottom of R17 to top of where W4 used to be. W4 was removed. Bottom of W4 has what looks like 47uf 16v cap going to top of R10 with I guess is R10 onto both legs of cap. Any Ideas what this is for???

Tele-Dave · January 29th, 2009, 03:26 AM

Reading schematic, looks like its being used to modify cathode power to both pre-amp tubes. Any ideas on this?

Tele-Dave · January 29th, 2009, 11:29 AM

Nobody?????????????????

muchxs · January 29th, 2009, 01:30 PM

O.k., I'm eyeballing the schematic. I'm not seeing "W4", though.

It looks like they decided a larger cathode bypass would be a good idea. There's an urban legend in circulation that "the largest possible cathode bypass is best", the theory is big cap = big bass.

It doesn't work that way in reality. It's possible to go way oversized on preamp cathode caps and end up with flabby farty bass. A lot of modern high gain amps go with 1-10 microfarads on the preamp cathodes. That's still a lot bigger than C4.

It seems the intent of your 16uf cap is to bypass R10. C4 (.068uf) bypasses R10, bright switch on, "drive" off. My guess is that the cleans might sound a little better but the overdrive will suffer.

http://www.diyguitarist.com/GuitarAmps/HRD_Mods.htm

Tele-Dave · January 30th, 2009, 12:54 AM

Quote:

Originally Posted by muchxs

O.k., I'm eyeballing the schematic. I'm not seeing "W4", though. ]

W4 is bottom right if u hold Parts layout with knobs pointing up in their natural position. Look at test point 4. Next component to left. What it is is a jumper wire. This might help!

Tele-Dave · January 30th, 2009, 04:35 AM

Any negative effects on tube life???

sjhusting · January 30th, 2009, 04:59 AM

I'm not finding W4 on the schematic either, but muchxs called it right as far as I can see; someone wanted more gain in the drive channel.

Shouldn't have any affect on tube life. How it sounds is your call.

steven

marshman · January 30th, 2009, 11:25 AM

MORE gain on drive channel?

Fer cryin' out loud, I could rarely use all the gain I did have...

Tele-Dave · January 30th, 2009, 04:02 PM

Quote:

Originally Posted by marshman

MORE gain on drive channel?

Fer cryin' out loud, I could rarely use all the gain I did have...

Yea I hear what u are saying. Drive is way too crunchy and bright. Going to remove this stuff and go back to way it was.

Changing out both of my input jacks. New ones are a little different from stock. No clear cover plate and the material feels a little different. Maybe Fender went with a different plastic so it will hold up a little better.

Wally · January 30th, 2009, 04:39 PM

TeleDAve, for my money I would suggest replacing those input jacks with old school Switchcraft shorting jacks. IT will be the last time you replace them. The stock arrangement of soldering plastic-housed jacks into the PCB is a sure way to guarantee eternal replacement, ime. IT is simple to figure out how to wire the Switchcrafts in.

Tele-Dave · January 30th, 2009, 05:04 PM

[quote=Wally;1647774].........I would suggest replacing those input jacks with Switchcraft...........QUOTE]

Had jacks so figured might as well use them. "Use only Genuine Chevy Parts"

Next time though................

Probably change out my plate load resistors also since Fender doesnt know which units got the bad ones. Can never be too careful.

sjhusting · January 30th, 2009, 05:12 PM

They fixed the plate load R problem by 2000.

If you use switchcraft jacks, you have to isolate them from the chassis, there are special washers for that (I use 'em anyway on all my builds)

steve

Tele-Dave · January 30th, 2009, 05:25 PM

Quote:

Originally Posted by sjhusting

They fixed the plate load R problem by 2000.

If you use switchcraft jacks, you have to isolate them from the chassis, there are special washers for that (I use 'em anyway on all my builds)

steve

Have parts, so might as well, since the iron is hot! Just feel like tinkering anyway.
Know about isolation on jacks. Thanks anyway for info. You don't always know who you're dealing with.

Here is old and new jack.

Tele-Dave · February 1st, 2009, 03:36 AM

Talked to a friend of mine who is a player (Twin Reverb) who is pretty sharp on electronics. He looked at the schematic and said that the mod will provide more boost and throw amp into distortion really early. That is exactly what it was doing. Didnt know any better myself because never played thru HRDLx before. I removed the mod and went back to stock. Dont know how much of improvment it will provide, but at least it is back to stock. Now I'm waiting on Mouser to del parts for some mods I want to do before I put it back together'

Going to replace 470ohm 1w screen resistors with 1Kohm 5w to prevent burnout incase i get a pwr tube short-out.
Going to do the Brightness mod following Justin Holton's suggestion.
Going to change Bass and Treb caps to alter tone curves

Once I do these mods I will start working on getting cleaner headroom

January 29th, 2009, 02:01 AM	#1 (permalink)
Tele-Dave Tele-Meister Join Date: Jan 2009 Location: Location: Location: West Virginia Posts: 320	Hotrod Deluxe Wiring question??? On my $200 pawn shop find HRDLx i noticed a strange wiring addition the previous owner must have installed. If anyone has a schem and parts layout, please follow along help me decipher this. There is a wire from bottom of R17 to top of where W4 used to be. W4 was removed. Bottom of W4 has what looks like 47uf 16v cap going to top of R10 with I guess is R10 onto both legs of cap. Any Ideas what this is for??? __________________ _____________________________________________ "no complaints yet, but it's still early"!!!

January 29th, 2009, 03:26 AM	#2 (permalink)
Tele-Dave Tele-Meister Join Date: Jan 2009 Location: Location: Location: West Virginia Posts: 320	Reading schematic, looks like its being used to modify cathode power to both pre-amp tubes. Any ideas on this? __________________ _____________________________________________ "no complaints yet, but it's still early"!!!

January 29th, 2009, 11:29 AM	#3 (permalink)
Tele-Dave Tele-Meister Join Date: Jan 2009 Location: Location: Location: West Virginia Posts: 320	Nobody????????????????? __________________ _____________________________________________ "no complaints yet, but it's still early"!!!

January 30th, 2009, 04:35 AM	#6 (permalink)
Tele-Dave Tele-Meister Join Date: Jan 2009 Location: Location: Location: West Virginia Posts: 320	Any negative effects on tube life??? __________________ _____________________________________________ "no complaints yet, but it's still early"!!!

January 30th, 2009, 04:59 AM	#7 (permalink)
sjhusting Tele-Holic Join Date: Jul 2003 Location: Germany Posts: 950 16 Photos	I'm not finding W4 on the schematic either, but muchxs called it right as far as I can see; someone wanted more gain in the drive channel. Shouldn't have any affect on tube life. How it sounds is your call. steven __________________ "When you have to kill a man it costs nothing to be polite" - WSC

January 29th, 2009, 01:30 PM	#4 (permalink)
muchxs Tele-Afflicted Join Date: Aug 2004 Location: New England Posts: 1,219	O.k., I'm eyeballing the schematic. I'm not seeing "W4", though. It looks like they decided a larger cathode bypass would be a good idea. There's an urban legend in circulation that "the largest possible cathode bypass is best", the theory is big cap = big bass. It doesn't work that way in reality. It's possible to go way oversized on preamp cathode caps and end up with flabby farty bass. A lot of modern high gain amps go with 1-10 microfarads on the preamp cathodes. That's still a lot bigger than C4. It seems the intent of your 16uf cap is to bypass R10. C4 (.068uf) bypasses R10, bright switch on, "drive" off. My guess is that the cleans might sound a little better but the overdrive will suffer. http://www.diyguitarist.com/GuitarAmps/HRD_Mods.htm

January 30th, 2009, 11:25 AM	#8 (permalink)
marshman Friend of Leo's Join Date: Feb 2007 Location: SE PA Age: 41 Posts: 2,011	MORE gain on drive channel? Fer cryin' out loud, I could rarely use all the gain I did have... __________________ 42

January 30th, 2009, 04:39 PM	#10 (permalink)
Wally Poster Extraordinaire Join Date: Mar 2003 Location: Lubbock, TX Posts: 6,010	TeleDAve, for my money I would suggest replacing those input jacks with old school Switchcraft shorting jacks. IT will be the last time you replace them. The stock arrangement of soldering plastic-housed jacks into the PCB is a sure way to guarantee eternal replacement, ime. IT is simple to figure out how to wire the Switchcrafts in.

January 30th, 2009, 05:04 PM	#11 (permalink)
Tele-Dave Tele-Meister Join Date: Jan 2009 Location: Location: Location: West Virginia Posts: 320	[quote=Wally;1647774].........I would suggest replacing those input jacks with Switchcraft...........QUOTE] Had jacks so figured might as well use them. "Use only Genuine Chevy Parts" Next time though................ Probably change out my plate load resistors also since Fender doesnt know which units got the bad ones. Can never be too careful. __________________ _____________________________________________ "no complaints yet, but it's still early"!!!

January 30th, 2009, 05:12 PM	#12 (permalink)
sjhusting Tele-Holic Join Date: Jul 2003 Location: Germany Posts: 950 16 Photos	They fixed the plate load R problem by 2000. If you use switchcraft jacks, you have to isolate them from the chassis, there are special washers for that (I use 'em anyway on all my builds) steve __________________ "When you have to kill a man it costs nothing to be polite" - WSC

February 1st, 2009, 03:36 AM	#14 (permalink)
Tele-Dave Tele-Meister Join Date: Jan 2009 Location: Location: Location: West Virginia Posts: 320	Talked to a friend of mine who is a player (Twin Reverb) who is pretty sharp on electronics. He looked at the schematic and said that the mod will provide more boost and throw amp into distortion really early. That is exactly what it was doing. Didnt know any better myself because never played thru HRDLx before. I removed the mod and went back to stock. Dont know how much of improvment it will provide, but at least it is back to stock. Now I'm waiting on Mouser to del parts for some mods I want to do before I put it back together' Going to replace 470ohm 1w screen resistors with 1Kohm 5w to prevent burnout incase i get a pwr tube short-out. Going to do the Brightness mod following Justin Holton's suggestion. Going to change Bass and Treb caps to alter tone curves Once I do these mods I will start working on getting cleaner headroom __________________ _____________________________________________ "no complaints yet, but it's still early"!!!

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