Silverface Bandmaster Reverb in the shop! These amps are kind of off the radar of many guitar players. They are a nice amp, 40W, 2 6L6 with tube-driven Reverb and tremelo, what’s not too like?  🙂   I have seen a number of them come through the shop here. This one has old (and failing) electrolytic caps, some kind of extra choke (see last photo below) hacked-into the chassis (even though the choke is not doing anything, as it’s shorted by a wire) wonder what the history on this amp is? In any case, after replacing the electrolytic caps, installing a new, properly-grounded, AC power cord (for safety), and possibly changing the bias circuit from bias-balance-adjust to bias-adjust, I bet this will sound fantastic!

** Someone, who did repair work on this at some point in time, replaced the first two (main) power supply filter capacitors with a value that is half of what’s spec’d. No wonder the customer was complaining of weak bass response! Also, some of the caps are 50+ years old, one has sprung a leak (The yellow one), and the paper one has a dimple on the end of the cap that would have soon turned into a leak, and a failed power supply. See the bottom two photos in this post.

Into the shop walked a mint Silvertone “1434”. A really cool amp, two channels, two 12″ speakers. Nice! I have not yet seen one in such clean and pristine condition.

The power supply caps were failing. See photo below where if you look carefully you can see a bubble beginning to form (it’s a little dimple) on the end of one of one of the power supply caps. I had a Silvertone in here a few years ago where the had cap failed, shorted the choke to ground, and literally burned-up the choke. So, we’re not going to let that happen! The amps is going to have all new power supply filter caps installed, and I’ll also replace some Sangamo coupling caps that were leaking. All the old Silvertone amps I have ever seen here in the shop have had leaky coupling caps, and that causes all sorts of problems!

I love Princeton Reverbs…who wouldn’t?  🙂

This one; from the Silverface years. The bias filter cap was bad, which caused the output (power) tubes to be biased incorrectly, way too hot. Hard to tell how long it has been in this condition but the output tubes are bad, probably because they were running so hot for a long time.

Anyhow, this one needs a new bias filter cap, new output tubes and I think it would be wise to install new power supply filter capacitors since one important cap has already died.

It gives me a real sense of pleasure to bring these great amps back to life and working at 100%  !

An old 1960’s Ampeg B15 Portaflex in the shop.

Bad rectifier tube, and lots of corrosion, causing bad pin-to-socket contact. Also, someone in the past had mucked-around with the cathode bias resistor (and messed things up, the output tubes were roasting hot).This one needs a lot of clean-up work…but for now, the owner needs it tomorrow. So, bring it back to life, and get it ready, even if not up to it’s 100%, for the gig!

Check out the power supply and output transformers. Huge!

Ray from Houston Texas sent his Holland “L’il Jimi” in for repairs.

Holland was one of the earlier “boutique” hand-made amps that appeared in the 1990’s, they went out of business eventually, but, the amp is basically a high quality great sounding amp.

It was squeeling, and, some of the pots (potentiometers) weren’t working correctly.

As it turned-out, the amplifier chassis is aluminum. Aluminum is a great conductor, except, it oxidizes when exposed to air. And the oxidized layers do not conduct electricity. The builder of the amp had relied on the pots making good electrical contact with the chassis to establish the ground reference for the pots. After many (15-20) years, the pots no longer had a good (if any) ground connection. After repairs: Now, the chassis has been buffed to remove the oxidation (in a few key places) and non-ozidizing compound has been applied (to prevent oxides from forming) and the amp sounds great. Top it off with some NOS 6L6GC output tubes and a re-bias and this baby will soon be on its way back to Texas!

Hmm..June must be Vibrolux Reverb month here at Sunnyside!

This one: a 1969 Silverface. The owner brought it in due to an annoying “ticking” sound due to the vibrato (actually tremelo) circuit. Most Blackface and Silverface Fenders with the LDR (light dependent resistor) tremelo circuit have this problem to some degree.

Ever held an analog (battery powered) wristwatch near your guitar pickups (with guitar plugged into amp, and amp turned on)? Same thing happens more or less. The clock signal is feeding into the analog signal chain.

The tremelo (inthis type of Fender amplifier) uses an oscillator, in conjuction with the LDR, to create the pulsing volume effect. The problem is that the oscillator and LDR signals can couple into the rest of the circuitry. I have seen this so many times. But there are remedies….

This one is a whole lot quieter now!

A 1965 Vibrolux Reverb: My friend Tim has brought in this fine amp to be worked-on. As far as I can tell it has never been serviced, all the parts inside the amp are original (The tubes might just be original as well)! But the old electrolytic capacitors are failing and need to be replaced. See photos below of the big brown capacitors underneath the amp. Also, all the electrolytic preamp cathode-bypass inside the chassis will be replaced. The real showstopper was that the electrolytic bias capacitor was bad, causing all sorts of hum and mayhem! When I am doing this type of resoration work I also replace the screen grid resistors and the grid stopper resistors on the output tube sockets. Add a properly grounded 3-prong AC power cord and this amp will be brought back to life!  Once it is up and running, I’ll also check some of the plate resistors and pots. Nearly 50 years of deferred maintenance, getting done!

The bottom most (3rd) photo shows that the electrolytic caps are leaking (two of them) and the other two are showing signs of leaks beginning to develop a leak. So, all these caps are bad, not a surprise as they are not meant to last more than 15 years or so. With new power supply caps this great guitar amplifier is going to come to life!

Wow, I have been so busy I stopped advertising for a while. It did no good, the amps keep coming-in anyhow! This week, in for repairs and mods:

* DR. Z Maz 38 – making crackling noises

* Dr. Z Prescription ES (Extra Strength) – master volume mods

* 1965 Fender Pro Reverb – tremelo disconnect switch installed

* 1969 Fender Deluxe Reverb – Intermittant tremelo circuit behavior

*  1950’s Supro Spectator – In for a three-prong (safely grounded) AC power cord install.