Now NAD : SF Pro Reverb advice

Corvus

I'm going to look at a Silverface Pro Reverb, the seller says 69-70 but the chassis stamp seems to date it to 1974. It's A188xxx.

I can't get a clear picture on the circuits vs year, any major changes etc, sites seem to vary a lot in what they say. Some say 69-74 is pretty much the same. It doesn't have a master vol, no mid control.

The main thing is would it being 74 make it less desirable/valuable than a 69, is what it boils down to really.

Cheers for any insights.

Lebarque

I'm sure someone more knowledgeable than me will chip in, but most people seem to favour the non-master volume versions. Sounds like you know that already though. I had an early 70's Pro which sounded lovely after I changed the speakers. It was very heavy though and bl00dy loud. Pretty much the same as a twin reverb. Bought and sold it for about £750 a few years ago I seem to remember. I believe they go for about the same amount now. 

bbill335

Lebarque said:

IBought and sold it for about £750 a few years ago I seem to remember. I believe they go for about the same amount now. 

They should go for that but one look at eBay says that sense isn't prevailing when it comes to Pro Reverb prices.

ICBM

The Pro seems to finally be benefitting from no longer being seen as the 'poor man's Twin' and as a nice amp in its own right. It's always been one of my favourite models - in my opinion it's actually more of a 'double Deluxe' than a small Twin anyway, in sound terms - but without the tendency of the Deluxe to flub out at what for me is *just* too low a volume/bottom end combination.

That said, all SF Fenders are now potentially problematic and need to be approached with price caution, since they will all need a full filter cap job soon if it hasn't been done already, and many suffer from the notorious board-conductivity problem as well as just the usual signs of a long working life and often 'fix-it' repairs rather than being done properly, if they break down.

A '74 won't have the 'tail' logo, unless it's been changed, a '69 will. There are a couple of minor circuit differences, but it's one of the models that wasn't changed much. (Until 1976, anyway.)

xpia98jf

I would be more concerned about the originality of the components and condition and how it actually sounds than the year if you're talking about the non-master volume version.  

DJH83004

It sounds like it is likely to be the AA1069 circuit, and as you say the chassis dates to around '74. Whilst maybe not quite as desirable as the '68-69 drip edge, still a very nice amp. Due to the weight and volume, the big twins are not quite as popular as they once were, and I think prices do reflect that a little. 

mbe

I had a '73 Pro Reverb and it could match any drummer on 3-4 and 5 would start to break up. Above 6 it starts to compress and, depending on the speakers fitted, things start getting nasty. The clean sound is rich and sparkly, more scooped than the earlier blackface.

The serial number is a reliable indicator of age. Also original speaker codes can be deciphered for age as well as original transformer codes. The 68 silverface (known as drip-edge) had a chrome trim round the front of the speaker baffle and fetch a bit more despite the dubious improvements to the circuit which were sensibly improved on the later non-master volume amps.

These amps can develop the 'sniffles' if they have been kept in damp conditions. It 's like a white noise that comes and goes randomly and is caused by the wax fibre main circuit board absorbing moisture. Another foible is the tremolo circuit can develop a ticking sound. Any decent tech can sort these problems.

The mains filter capacitors are enclosed in a metal shield fixed to the chassis called the 'doghouse'. These caps must be replaced if they are over ten years old.

Ideally you should be able to hear it on 4 on the volume and you will definitely hear the wow factor if everything is healthy. Any over £500 should really be the Export model for 240 volts and not a US model with step-up transformer.

bbill335

ICBM said:

That said, all SF Fenders are now potentially problematic and need to be approached with price caution, since they will all need a full filter cap job soon if it hasn't been done already, and many suffer from the notorious board-conductivity problem as well as just the usual signs of a long working life and often 'fix-it' repairs rather than being done properly, if they break down.

I was due to buy a '73 Pro Reverb the other week. The day before the deal, I got a phone call saying it was playing up so the deal was on hold. Guy took it to his tech and whaddyaknow, conductive board. The Pro Reverb is basically my perfect gigging amp (although a Vibrolux or Super Reverb would probably be just as nice), it's just hard to find good examples sold by people who know what's happening inside.

Corvus

Many thanks all, I'll read up on the boad conductivity, I knew of it but that's all. The amp's supposed to have been serviced & maintained but I'm expecting to take it to someone to check over.

It has Utah speakers which seem not majorly loved but I've not hear them, or any before. It is a tail-less logo, and 240v, I'll give it a close look for signs of mods/bodges etc.

ICBM

mbe said:

The mains filter capacitors are enclosed in a metal shield fixed to the chassis called the 'doghouse'. These caps must be replaced if they are over ten years old.

I've read that a lot, and it's a wild exaggeration. Thirty years is more accurate, and even at that I wouldn't necessarily do it as a matter of course unless they've failed or the amp was getting a full overhaul anyway. I would certainly not change a cap at anything under 20 years old unless it's actually failed. Beyond about forty years, I would - which does include SF Fenders, even though the youngest are just under that.

It may once have been true, but from the 1980s onwards cap quality and lifespan increased markedly.

mbe

Mine had Utah speakers and they sounded really good. As I said earlier the speakers do have a bearing on headroom but I think the Utah speakers are certainly not deficient tonewise.

The other speakers fitted by Fender included Oxfords (sometimes called Oxfarts) and Pyle (sometimes called Pile of xxxp). I guess they are all judged by the Jensen, Weber and Rola Celestion drivers.

DJH83004

All good points from MBE and IC, the eyelet board conductivity problem in the vast majority of cases is sort-able, I personally have never failed on one yet, but do use some pretty expensive 3M Scotch isolator / sealer. A cap job is again a relatively straightforward job to do, just make sure the bias caps and cathode bypass caps are done as well as the power supply caps. If it is a US model, would strongly recommend the PT changed to UK voltage rather than step down transformer, less weight, less points of failure, less potential earthing / grounding issues. I personally use Hammond TX.     

Corvus

Thanks again guys, great stuff.

jpfamps

I used a SF Pro Reverb as my main amp for ages and they are great.

You want the earlier version with the valve rectifier, which this should be.

I don't think there is much difference in value in 69 - 74 in these amps. 

Main issues are mainly whether the cab in is good condition and whether the amp has suffered any hack repairs over the years.

Utah speakers are great, Oxfords less so. I've got a pair of reconed 60s C12Ns in mine.

If it hasn't been recapped then I would recommend getting this done.

You can also get this circuit converted to the BF circuit, which I think is an improvement.

jpfamps

Corvus said:

Many thanks all, I'll read up on the boad conductivity, I knew of it but that's all. The amp's supposed to have been serviced & maintained but I'm expecting to take it to someone to check over.

It has Utah speakers which seem not majorly loved but I've not hear them, or any before. It is a tail-less logo, and 240v, I'll give it a close look for signs of mods/bodges etc.

Utahs are my preferred speaker in SF amps and sound great.

I've worked on 100's of SF / BF amps amp and rarely have I found board conduction to be a problem; in my opinion this seems to be a problem invented by techs as a way of increasing the repair bill, especially if they recommend replacing the board itself!

The only area of the PCB where DC leakage is a common problem is around the 3.3M (sometime 4.7M) mix resistor in the reverb recovery / mixing stage. With such a high resistance a small DC leakage will cause problems, however this is easy to fix by lifting the resistor and surrounding circuitry of the board and onto some tag strip.

Ultimately if the amp is working fine with no odd noises it can be made to work reliably.

DJH83004

I do think there are genuine instances with crackles and pops are caused by DC leakage on the board JPF, I've had it on a number of my own BF & SF amps over the years, but easily solved my carefully separating the eyelet and insulation board and spraying (even WD40 is quite effective!), I have also put nylon washers between the boards, at the screw holes to provide physical separation as belt and braces, and it does does quieten them down.     

ICBM

I did a Twin last week where it was causing trouble around the 3M3 resistor - causing nasty distortion on the Vibrato channel by forward-biasing V4. I have also sometimes lifted the components onto a tag strip, although this one was (as it often is) caused by the underlayer board rather than the actual eyelet board, so the good old Cornflake box trick fixed it. I have also never come across one that couldn't be fixed with one or other method, or a combination of them in extreme cases.

I've also had several Musicmaster Bass amps which have trouble around the input resistors and cap - which makes the usual hum and buzz worse - but this is a poorly-laid-out amp anyway, and I suspect that being cheap they didn't pay as much attention as they should have.

Lebarque

I forgot to mention - My old SF Pro came with a rather nice old Mullard valve rectifier under the hood. Safe to say it stayed with me when the amp got moved on. :0)

JohnPerry

My Deluxe Reverb had the board conductivity problem and, after Mr ICBM's generous counsel, I fixed it myself with a strip of plastic ripped from a diary. Worked a treat. Two years of crackles solved in ten minutes.

Corvus

So it did become a NAD -

http://alleykat.co.uk/images/stuff/pro_reverb/pro_reverb1.jpg

All seems good, it's very quiet, sounds great.. only been run to 3 so far, can't wait to give it more beans.

There's a slight ticking from the vibrato, a fairly quiet tick, but I'll have it all looked over.

Corvus

It's set to 230v, I haven't tried 240 yet, wonder if any difference could be heard.

http://alleykat.co.uk/images/stuff/pro_reverb/voltage_switch.jpg

The one unknown is this switch added to the rear, the last owner didn't know what it's for and I haven't tried. I'll pop the chassis out on the offchance I can work it out but I'm a long way from being able to read circuits

http://alleykat.co.uk/images/stuff/pro_reverb/pr_switch.jpg