Phonoland

hey gang! my recap kit from Victory arrived. i'm an amateur tech... my soldering chops have gone dormant as my music gigs have gotten busier. but i do work on my old guitar amps on occasion.

just checking to see if there's anything to be especially careful of... i've never "shotgunned" a circuit full of 20 caps before, i usually just fix what breaks. i'm gonna be careful and take my time with each joint. but i'm just a bit apprehensive about doing them all at once... one little error could turn into a big mystery. but it also seems like the thing to do, and then have a fairly clean slate for diagnosing the mech and controls. yes?

cheers,
eric

Eric,
The "paper" cap between the relays must be handled with care when removing--the relay terminals will tolorate ZERO heat/twisting--
Ron Rich

thanks, Ron! i see a molded one in between, and a paper/cardboard one along side one of the relays. i'll just be careful with my iron in that area.

cheers,
eric

Oh - and what's a good way for me to discharge these big caps? i don't have any big resistors around my apt. ??

on my tube amps i will drain through the first preamp tube's plate, which gives a nice steady discharge that doesn't go too fast or too slow. but i don't really know this tormat circuit.


...and while i got your 'ear' - do i need to worry about the solid state rectifier due to age? i will often replace old recto tubes as they are often cheap and easy to do. but this thing is weird to me!

Don't need to--they self discharge--
Rectifier is probably OK if paint has not "bubbled"--change fuse from 15 to 7.5 amp
Ron Rich

ah, life gets a little easier - thanks!

has anyone ever tried a solid state replacement/equivalent for the 6X4 tube? a very affordable option... but does it affect the voltages... could be more reliable than old stock tube.

Yep--Seeburg made it on the next model--would interchange except that they used a newer type plug--
Ron Rich

I have long used silicon diode, two in-series and an approx 5watt resistor of 190-300 ohms and a 500ma/fast fuse in place of the 6X4.

The diodes are usually 600 volt and 1 amp or greater. two are used just for added protection in case one shorts. I've done this since 1988 and several of those are still in service.

Even if you don't replace the 6X4 you should add the fuse inline with pin 7 (cathode). Those tubes are known (to me) to be transformer killers.

Rob/NYC

Rob-NYC wrote:I have long used silicon diode, two in-series and an approx 5watt resistor of 190-300 ohms and a 500ma/fast fuse in place of the 6X4.

The diodes are usually 600 volt and 1 amp or greater. two are used just for added protection in case one shorts. I've done this since 1988 and several of those are still in service.

Even if you don't replace the 6X4 you should add the fuse inline with pin 7 (cathode). Those tubes are known (to me) to be transformer killers.

Rob/NYC

Supplies using those 6X4's - I usually replace them with 1N5408's (3A, 1000V) and call it a day.
Never have to worry about rectifiers again.

gotcha - thanky! i was gonna order a SS plug-in replacement, which i imagine contains the diodes y'all mention (i'm a musician, not a real tech...) is that probably the case? here it is:
http://www.ebay.com/itm/6X4-X1DR-Solid- ... SwVL1WAE~R

does the SS approach end up raising the B+ voltage? you know, one less filament? is that what the 5 watt resistor is for?


meanwhile - today i found a JAN 6X4WA in my studio tube stash - the mil-spec version of the tube. it has seen very little use and tests well. i'll probably just go with that, and Rob's fuse idea off of the cathode pin lug. i don't have any silicon diodes on hand but i might order up some in my next batch of components.

does the SS approach end up raising the B+ voltage? you know, one less filament? is that what the 5 watt resistor is for?

Yes, it does raise the B+ but it has nothing to do with the filament current. It is just that the SS rect's have much lower forward drop (internal resistance).

A resistor is important here as this is a tightly regulated part of the circuit and the 0A2 reg's are operated at their correct firing voltage (300VDC ÷ 2 tubes ea @150V).

Rob

finally getting the last of the caps in. slow going due to my holiday gig schedule, and novice tech skills...

should i do my first power-up on the variac? these are all new caps. if so, how gradually?

cheers,
eric

Hi Eric,
Not a bad idea--30--60--90-117 volts--or use a sixty watt light bulb in series with the input AC--You do realize that changing caps, won't fix any other problems that you may have in that unit--
Ron Rich

babycat wrote:finally getting the last of the caps in. slow going due to my holiday gig schedule, and novice tech skills...
should i do my first power-up on the variac? these are all new caps. if so, how gradually?
cheers, eric

Eric, the single most important thing you can do now is to --check and double check the polarity of the electrolytic caps you have replaced--.

This system uses the caps -positive ground-. I have seen several cases including a TSR-3 that I bought where the transformer was ruined by backwards caps shorting-popping and killing the tran. The guy I bought it from was an 'expert" in pinballs and had "done some jukes too"-he obviously thought this was conventional negative-ground.

Rob