The correct replacement is an Accutronics 4FB2C1A. I have not seen the new Korean made tanks or tried them in a Kustom head yet, so I don't how well they work, but there are still NOS US made ones out there.
Holy Crap!!! The 4 F B has 1475 ohms in and 2250 ohms out. I thought they wanted to see 180 ohms in and out. I've been replacing them with a short tank type 1. Got one here in my hand typical to what I use and it is testing out at 200 ohms in and 175 out. The result I get is a real (Fender Twin Type Reverb)deeeeeeeep reverb ability and if you locate it correctly in the chassis or cabinet top of the Frank models it doesn't hum or squeal when ya turn it up. I got 2 Franks here I've restored and have it in both. I like the longer Type 4 or 9 for overall sound but the short 1 or 8 is working pretty good for me. I'm not a tech by no means but I thought I could share some options I found useing vintage parts I find all the time on ebay. I do notice sometimes I have to ground the tank to the chassis to get it to work and other times I dont depending on the connector design of the reverb. For instance I like the (MOD 8BB2A1B) ones I get off Ebay with the Medium Decay even though the mounting plane is usualy B on those suitable for me. The grounds can be lifted to suit the circuit just by unsoldering the junction on the inside of the RCA jacks. Output impedance is more that I thought I wanted but it works fine. Well thats my penny and a halfs worth. Steve C
You learn something new every day. Thanks, I didn't know that. I guess the next question would be what is impedance and how do you test it? I was under the assumption resistance and impedance both meant the same thing, to resist or impeed meaning the same thing.
The short answer is that impedance deals with ac signal loads, dc resistance deals with dc voltage.
To measure impedance you need to inject an ac signal into a load with a series resistor and measure the signal drop. I'd have to look up the specifics to give a more accurate formula and test procedure.
OK, that all sounds pretty complicated except for the Acutronics chart. I guess so far I've been lucky. I always try to get one with low ohms at input and output thinking 180 ohms as my target on input and output. Is it damaging to the circuitry if the impedance is wrong or will it just effect the performance of that circuit?
Kustom_Bart Messages: 601 Registered: October 2010 Location: Greenville, MichiGUN
Senior Member
You guys are waaaaay over my head, but I love reading this stuff and locking it into the memory bank...lol! Good stuff!
I have a tough time reading a schematic but I am getting better. I have a guy here about 2 miles away that is a old timer tech that does all kinds of weird stuff...the more strange it is the better he likes it. Juke boxes, old Fender and Kustom amps, boards, powered and non powered, old bar video games etc. I have known him since I was about 5 yrs old. He was friends with my dad. He takes pretty good care of me as I always bring him cool stuff to repair and a schematic. normal cost is about 40.00 to repair a Kustom.
I have tried to get him to let me come and help him to learn something as he keeps saying he is going to retire....but he is hesitant to do so.
Well if the impedance is mismatched there will be a loss of signal strength and frequency response. Have you ever tried plugging in a low impedance mike into the front of a Kustom amp without a matching transformer?
If you use the wrong tank it won't hurt anything electronically, but it will either not sound right or it won't pass signal at all.