301 retnev 1 year ago You can use the variac in the mean time to bring the vox up. That serves the same purpose of a brimistor as anti-surge, but not for filtering which the brimistor is alsio involved in. As a preferred temporary fix you can add a 3-6 Ohm 5W wirewound or composite resistor in the place of the brimistor just to help the capacitor filter. However, it would be great if you pause the work until you get the brimistor or add the 5ohm 5Watt as things will not really work right until you have that installed.With the short you now dont have an RC filter but the capacitor just acts like an AC shunt, which is ok but it s noisier. The RC filter cutoff equation is f=1/(2 * Pi * R * C) and if R tends to 0 you can clearly see that the frequency goes way past 50Hz to infinity, so technically no filtering at 50Hz. You then only rely on the capacitor to short AC as a shunt, which is not ideal.So the resistance or brimistor is needed.A shunt is usually sufficient, but not as effective reducing hum so you need the RC network of which the Brimistor is part of. There are lots of shunt based power supplies which works perfectly well enough but they will have more hum than RC based power supplies. Denney tried to do it right. Without at least some series resistance, The capacitor cannot properly get rid of the hum, it needs a series resistance to effectively filter the ripple. At the moment you have a short circuit which in effect makes the RC low pass filter only a capacitor in parallel. The Brimistor that used to be in there, supplied the series resistance and also gives you slow ramp up. The amp was designed like that for good reason.I havent received the brimistor equivalents yet it is on its way and was shipped. It should be a nice solution. They are likely nos military surplus from 60s as they break down old equipment out of service here in the US and I always look out for what I need. I will ship it as soon as I received it and verified it. I sen it for free, no charge. It has been giving you trouble for decades without resolution when it was serviced, so a little bit of wait should not be such a big issue right ?There are a lot of brimistors and surgistors in the old equipment, but people usually dont know what they are as they usually have no markings due to heat and aging and or usual custom components with unobtanium codes. Out of the handful I will match one for the AC50 and test it here. From what the person I got it from measured when I asked , they seem to be spot on. These seems to be spares that was kept with equipment as surgistors and brimistors took the brunt of faults and fail predictably as they should protecting the equipment.The problem with the gap in the speaker is that if any filings or ferrous pieces go in there it is almost impossible to remove, as they are attracted to the magnetized side. The only way to remove that is to remove the magnet. I agree with his concern. That said, though it is far from the end of the world he will always give you a worst case outlook. Dont feel down by that. He is just correctly giving you the worst case scenario. I would have done the same. However, you can be sure that after a while there will be no scratches from that at all. They will align on the side.Dust cap removal is what I expected. There you see what happens when someone not using the correct materials works on a speaker. Sounds like they used epoxy. There are three very specific completely reversible glues you need to use for coil, cap, damper and basket edges. You are in good hands, he knows what he is doing.