A SAD & DAMP STORY................


After a pre-arrangement on the phone of a day and time, a young man (Adrian) and his father paid me a visit from Nuneaton, Leicestershire. Adrian had a Fenton-Weill Porta-Bass 15 head with a sad story behind it. This amplifier had apparently stood in someone’s shed for about 10 years or more. Now..... not only is a shed a very damp place and not the type of place one should store delicate electronic equipment but, in this case, water had actually been running into the top of the amplifier too!


Adrian continued his story explaining that when he acquired the unit, complete with its matching speaker cabinet, it was all covered in mildew He had cleaned-up both units thoroughly and fully dried them out before proceeding to try them out. The amplifier lit-up OK, but after about 20 minutes there was a loud bang from the underside of the amp. Rushing to the power socket, he disconnected it rather promptly and then took the old amp to two or three "modern-day" technicians, all of whom basically refused to work on it! He then proceeded to search the net for someone with the "know-how" on this type of equipment. Upon finding this website, he then made the said phone call.


On first examination of the unit it was blatantly obvious that one of the main smoothing capacitors had blown itself apart! This actually is quite a normal and common occurrence on high-voltage tube (valve) amplifiers after they have stood for a very long time. The capacitors dry out and then, when they are hit with the voltage again, they get hot and eventually blow out the electrolyte. This can be very dangerous if someone is standing in the sight-line of such capacitors; they usually shoot one of the ends off with some tremendous force and speed! I blobbed a couple of new ones on whilst Adrian and his father were in the workshop; just to see if in actual fact it would power up and at least do something? This it did with about 3 watts showing on the test gear, and a most dreadful picture on the scope too! ......Not surprising at all.


After bidding Adrian and his father farewell, I left the unit on for a couple of hours just to see if the very rusty power transformer had sustained any permanent damage through all the water ingress? It turned out to be fine, which was very lucky. Although I had a couple of other repairs in the wings (but not urgent), as this amp was now on the bench I just decided to continue with it.

After the initial examination, the following faults were apparent:

On closer scrutinizing the following major problems were found too: 

Basic restoration tasks additional to the above included: 





About a full weekends work……….Phew!

This one was quite a challenge but I don’t let things beat me. All good fun though!


She’s now all back to life, working well, and at 15.98 watts too. That's actually better than it would have been with the original 6BW6’s; this model usually makes about 12 watts RMS before clipping.

By the way, this Porta-Bass has the date of 7/8/64 written inside the chassis. The amp, or maybe just the PCB, was presumably assembled by Joan, who has written her name on the circuit board. See the two photos below:



Left, the date 7/8/64 written on the chassis and Right, Joan's "mark".

Click HERE to see another Porta-Bass 15 that I serviced some time ago; still original and un-touched. That one wasn’t quite so sad!

Cheers for looking, John.


And the final comment from Adrian, the amp's owner:

"Hi John,
Dont know if you remember me. You repaired my Fenton Weill Porta-Bass amplifier for me. Just thought I'd say thanks for your hard work and also to send you a photo of the finished re-covered amp in full working order.
Thanks again,