NVAD 73 Quad Reverb hatchet job

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NVAD 73 Quad Reverb hatchet job

Post by tubeswell »

New wee restoration project in need of some TLC (in case I run out of things to do with the rest of my life).

I'll run it with my Dual Showman cab.
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Re: NVAD 73 Quad Reverb hatchet job

Post by tubeswell »

So some silly ass has gone to the trouble of installing a bucking PT for the bias supply, but no-one has ever bothered to replace the filter caps. (I mean, why not just get a new PT if there was a voltage problem? 1st thing they should've replaced was those old filter caps, So methinks the PT might be rooted because someone wanted to keep the caps 'original'. But there is sooo much other carnage inside.) Duh....
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Re: NVAD 73 Quad Reverb hatchet job

Post by Bg »

:oh: you're allowed to say fucking you know ;) Maybe wanted to keep costs down by not replacing the whole thing just for the bias voltage? Anyway, I'm sure you'll be relishing getting your teeth into that amp ;) Don't pretend you aren't!
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

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Re: NVAD 73 Quad Reverb hatchet job

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Jesus

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Re: NVAD 73 Quad Reverb hatchet job

Post by tubeswell »

You understand me BG
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Re: NVAD 73 Quad Reverb hatchet job

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Super excellent fun times !

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Re: NVAD 73 Quad Reverb hatchet job

Post by RectifiedAmps »

At least they didn't try to 'fix' the symptoms of no bias by replacing the mains fuse with a bit of rolled up foil. Seen that a few too many times...

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Re: NVAD 73 Quad Reverb hatchet job

Post by tubeswell »

RectifiedAmps wrote:At least they didn't try to 'fix' the symptoms of no bias by replacing the mains fuse with a bit of rolled up foil. Seen that a few too many times...
Its got the wrong value mains fuse'n'all
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Re: NVAD 73 Quad Reverb hatchet job

Post by Bg »

RectifiedAmps wrote:At least they didn't try to 'fix' the symptoms of no bias by replacing the mains fuse with a bit of rolled up foil. Seen that a few too many times...
Or a nail....
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

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Re: NVAD 73 Quad Reverb hatchet job

Post by tubeswell »

Wee update. At some stage in the past the lamp holder's insulating cork had cooked, leaving charred contacts. The lamp had been disconnected from the heater winding. Also one of the 6L6 1R cathode current measuring resistors was fried, so it seems that there was a power tube failure. I did't trust the old lamp holder nor the 6L6 sockets, so I replaced them with new parts, and generally cleaned up around the chassis with isopropyl. (I even reused the former 'as-found' wiring :) ) I also re-did the crappy SF soldered-PT-bolt chassis mains ground with a proper crimped ring terminal lock-nutted to a dedicated chassis bolt. I also replaced the filter caps with new FTs, and replaced all the other e-caps inside the chassis, but the rest of it is stock for the time being. However, I'm suspicious of the old SF waxed eyelet board. Sometime in the past someone has jumped several components off the board, and have even remounted part of the PI circuit onto a tag terminal strip. Methinks I'll replace the main board eventually and remove all these lazy band-aid fixes. Also I'll keep the post PIMV mod for the time being, but will re-visit at all that if I end up re-doing the main eyelet board.

I'm also leaning towards a replacement PT. I disconnected and tested the PT and bias bucking transformer combo, and they are functional with ballpark AC on the secondaries. The bias DC supply with new e-caps and a diode works but the funky Dick Smith 50k pot gives way-too-big-a range (-27 to -59VDC, which I find a PITA when dialing in bias). However, something bad did happen (in the past) with the old lamp circuit and something fried one of the 6L6s, and for some reason they whacked in a bucking tranny for the bias supply, which all adds up to power supply issues. So methinks the 73 vintage PT may have to go :cry: Time will tell about the PT when I fire it up with a new quad of 6L6s.

On the positive front, the vintage OT passes the requisite Pr:Sec VAC ratio (and is evenly matched on both sides of the Primary), so being able to keep that will be good for the sonic mojo. At this point I have to say on the whole, not a bad score for 5-hand shandy, even if I have to replace the PT.
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Last edited by tubeswell on Sun Nov 26, 2017 12:40 pm, edited 2 times in total.
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Re: NVAD 73 Quad Reverb hatchet job

Post by Single coil »

I understood some of that :mental:
werdna wrote:Well at least I can still make toast in the bath without anyone telling me it's unsafe.

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Re: NVAD 73 Quad Reverb hatchet job

Post by Dharmajester »

All I got was that I'm allowed to say fuck .
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Re: NVAD 73 Quad Reverb hatchet job

Post by StrummersOfThunder »

I have plenty of left over beautiful black garolite board tucked away that I got of another forumite some years back when I was building my princeton reverb.

Much nicer than that wobbly card stuff. Let me know if end up redoing the board and need/want some :)

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Re: NVAD 73 Quad Reverb hatchet job

Post by tubeswell »

Tolexed my DIY head cab 2-day. Got some Silverface grille cloth in the post. Hunting for a 73-era Fender logo for the front.
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Re: NVAD 73 Quad Reverb hatchet job

Post by Bg »

very cool :)
So, is that low alcohol or no alcohol at all? mmmm, no alcohol, do you want to try it? Noooooooooo.

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