Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: chrisq on February 18, 2013, 04:05:34 pm
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Hi!
You all have been so helpful! Thanks! I have one last favor...
So, this 1484 was hardwired. I've removed the speaker line and installed a 1/4 jack on the cab, made a speaker line out of the old wire and I am now in the process of installing a 1/4 jack on the head.
While I was doing the rest. The marker for the negative side of the line coming from the amp fell off...
Inside there is a tap. One side is yellow, one is black one is red and yellow and not hooked up.
I believe that the yellow is the positive (that goes to the tip) black is the negative (that goes to ring) and the other is a 8ohm tap.
So as of right now I have...
Red dot on speaker>tip on jack>1/4 plug tip>wire>1/4 plug tip>tip on jack>yellow wire
Black wire on speakers>ring>1/4 plug ring>wire>1/4 plug ring>ring on jack>black wire =no fire/smoke/expensive repairs ;)
Just to also clarify. The 1/4 plugs have one short (positive) and one long (negative) posts right?
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<00000==___ If you follow my drawing.
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Am I right???
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Also... do I need to insulate the jack from the chassis. Or is metal on metal ok?
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Am I right???
Yes, thats right, except for your terminology. There is no ring with a simple one circuit (mono) plug such as most speaker plugs. What you called a 'ring' is actually a 'sleeve'. Ring is a term that applies to 2 circuit plugs (stereo). See the pic...
No need to insulate the jack from chassis.
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yes! I meant sleeve! thank you!
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And exact speaker phasing is meaningless unless you have multiple speakers hooked up to this amp, or have your guitar signal split among several amps.
Even in the latter case, it still might not matter, because there's no guarantee every amp outputs a positive wave for a positive input (that is, on the whole an amp may invert the signal or not).
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i bought one off CL last week with known issues - the reverb tank is tanked. output coil reads infinity. going to attempt to shoehorn in a MOD tank.
how do you like yours? other than brief testing when i bought it, i haven't played on this one enough to form an opinion.
--pete
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I just finished a 1484 head rescue--- bought it late last yr --- was inop/needs work--- work done in stages between other people's amp work.
New stuff:
Power cord (3 prong grounded)
Power Switch (orig flakey)
Speaker output jack (had orig lamp cord-- @18 inches-- no plug)
Axial filter and bias caps
Rectifier and bias diodes
V4 tube socket (orig didn't respond to clean/retension)
Preamp and reverb bypass caps (ended up with 4.7uF for both after tying different values--- orig Red Planets drifted to @60uF from stock 25uF)
Many orig drifted resistors changed-- including new 220k carbon films for V1 plate load resistors--- less hiss than origs that had also drifted up to 260k.
Has orig OT--- trem works--- reverb works after much effort, replacing V4 tube socket, many components mounted on V4 socket--- running an RCA 12au7a in V4 to help control crazy reverb runaway--- also installed a 22k grid resistor on V4a mostly to lengthen orig shielded cable after tube socket replacement but also to help control reverb runaway/slight oscillation---- re-attached both wires leading to reverb tank (looks like they were mouse chewed)---- now reverb is usable, not great, but usable--- and it's stable--- about the best that can be hoped for with the orig 1484 reverb----amp sounds better using a delay pedal, but oh well- :dontknow:
So now it's a good sounding and properly working 1484--- i've re-done many of these 1484's and usually the OT is blown and the reverb doesn't work (no big loss with this reverb design).
It's fun to play thru a 4 ohm 4x12 loaded with WGS ET65's---- clean up to 4 and then it starts to give up the 1484 crunch--- tomorrow I'll A/B it against my BF Vibrolux Reverb replica thru the same 4 ohm 4x12 cab and see how they match up...............................gldtp99
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Hi!
You all have been so helpful! Thanks! I have one last favor...
So, this 1484 was hardwired. I've removed the speaker line and installed a 1/4 jack on the cab, made a speaker line out of the old wire and I am now in the process of installing a 1/4 jack on the head.
While I was doing the rest. The marker for the negative side of the line coming from the amp fell off...
Inside there is a tap. One side is yellow, one is black one is red and yellow and not hooked up.
I believe that the yellow is the positive (that goes to the tip) black is the negative (that goes to ring) and the other is a 8ohm tap.
So as of right now I have...
Red dot on speaker>tip on jack>1/4 plug tip>wire>1/4 plug tip>tip on jack>yellow wire
Black wire on speakers>ring>1/4 plug ring>wire>1/4 plug ring>ring on jack>black wire =no fire/smoke/expensive repairs ;)
Just to also clarify. The 1/4 plugs have one short (positive) and one long (negative) posts right?
+
<00000==___ If you follow my drawing.
-
Am I right???
The stock Silvertone 1484 is hardwired and uses the 4 ohm tap which is the yellow wire. The red/yellow wire is the 2.6 ohm tap and was used on the 1485. It is not an 8 ohm tap. The 1485 used two OT's identical to the single one that is in the 1484 and there were wires going to the speaker cabinet which had 6 eight ohm speakers in it for a total load of 2.6 ohms for each tap. Black is ground. You could install two jacks and have one 4 ohm and one 2.6 ohm jack on the back of your amp. You can run the 2.6 ohm instead of the 4 ohm if you want for a different sound. The OT is very small but it can tolerate that small mismatch just fine. It will even work fine with the 4 ohm tap going into an 8 ohm speaker, though the sound changes when you mismatch and the best headroom is a 4 ohm speaker into a 4 ohm tap or a 2.6 ohm load into the 2.6 ohm tap.
Greg