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Discussion in 'Amps and Cabs [BG]' started by notforrobots, Jan 23, 2009.
Hey Jerrold, what do you think about the fliptops cap kit?
I ordered one but didn't replaced the originals yet.
i'm not Jerrold but Bruce at fliptops has some new caps-70/40/40uf that would be the exact filter caps for an SVT. his is currently updating his kits to use them, so the Fliptops kits will work perfectly in an old SVT. he also offers a 25uf @ 800V cap to replace the 30uf/600V cap which will also work well.
Antique Electronics (www.tubesandmore.com) has the multicaps you need.
Bassmec when redoing the power caps on an amp with a tube rectifier you have to remeber that the tube is limited in the capacitance it can drive. The GZ34/5AR4 can only use 30µF in a capacitor input supply. More than that and you can get flashover and destroy the tube.
look up high-pass, low-pass, band-pass, and band-reject filters.
he's talking about making the filters more capacitive lowering the cutoff frequencies (half power point).
its all RLC circuits. read up on it
Sorry Jimmy but your post makes no sense to me. Kindly explain where you are trying to go.
I say go for the bigger capacitors.
There will be a bigger instantaneous surge when you turn the amp on
but, unless the rectifiers are operating on their very edge now (not
likely), it shouldn't be a problem.
The average current through the rectifiers does not change. The amp
is still drawing the same amount of power through the circuit. The
rectifiers will dissipate the same amount of power that they did before.
Generally speaking, when engineers choose electrolytic capacitors (the
big ones) for a power supply design, it is not uncommon to choose the
smallest value you can get away with. It saves space and cost. The
technology has improved. Capacitors are smaller today and, if you're
going through the trouble of replacing them, you probably don't care
about the nominal extra cost of the bigger ones.
i always stay as close to the original amp's values as possible. as Jerrold said, what works in theory (higher values) can "stiffen" the amp's sound. i have seen this too many times when repairing old Fender amps that have been serviced by 'techs' that don't understand what they are supposed to sound like (putting in larger values). alot of 'electronics' guys seem to think that its okay to raise the values, but most good tube amp techs see it as a no-no.
I just received the cap kit from fliptops.
I opened my amp to look inside of it, I'm not a tech but a friend of mine is and he already supervised me once to recap an old marshall, he's confident enough that I can do it by myself, I know how to work in a tube amp so no worry, I won't kill myself, I already emptied (uncharged) the caps.
Here's what was inside my amp (I think one or more as been replaced):
Blue: 90MDF 200VDC
1st Yellow: 30-600DC
Brown: 100MDF 450VDC
2nd yellow: 100uF 450VDC
1st underside can (we dont see those on the pic): can't read it...
2nd underside can: 10/10MDF 450/450VDC
And here's what was in the fliptops kit:
I've written them in the order I think they should go, example, 100uF 350V would replace Blue: 90MDF 200VDC.
What do you think, I'm a little bit worried about the 25uF instead of 30uF on the 1st yellow....
Let me know what you think.
the 25uf cap instead of the 30 uf works perfectly.
That's what my tech told me, just wanted to confirm.
Otherwise, what do you think about those replacement?
I guess I'll hear it myself but I'm eager to know
You will love it!
At least I love mine after this recap.
Better focused bass, stronger mids and NO HUM.
Bruce serviced hundreds of SVTs and he KNOWS whats the best subtstitute for the old cans.
Higher capacitance would just spoil the trademark-sound of an svt.
Look forward to it and WATCH THE POLARITY when soldering them into the circuit.
The only think I know, is that if you take apart a disposable camera, and then you charge up the camera's flash, it charges the capacitor. Since the case is off, you can take a screwdriver or knife and lay it on the camera's connectors next to the flash and it goes BOOOOOM! and sparks fly everywhere and is a good scare. It melted 2 small holes in my pocket knife.
This is the extent of my knowledge of capacitors.
Probably didn't help, but I thought I would share
Although I agree with the general sentiment of this statement, it is misleading and not entirely true. CBS did upgrade some of the parts in the silverface amps when they took over the company, but more importantly they also changed Leos original circuit designs in order to increase clean headroom. The biggest tonal difference by far is a result of changes in the circuit, not just the parts. You can claim that the changes "weren't significant" because the schematic looks mostly the same, but having modded a silverface amp to blackface specs, I can say for certain that the changes to the circuit they made have a quite significant impact on tone.
I'm not so sure about this one, what is the 47uF 450V suposed to replaced in the list I gave in my last message?
Agree with you completely.
It seems to me that this 100uF 450V misterious cap was added by someone else, probably to either mod the amp or to replace one side of a multicap that would have been defect.
Does it make sence?
Is there suposed to have 5 or 6 caps in the power section of the amp?
my '69 and '75 SVT's have five filter capacitors in the power supply, but two of them are dual caps, making a total of seven.
I've got two dual cab too which are outside of the chassis, close to the transformer.
I'm pretty sure tha 6th cap that was in there was some sort of fast repair.
It's not the only thing to look like it was repaired in a rush...
I'll bring the cap to my tech today and mesure them to see if one of the double one is defect or something...that might help to investigate.
I need to recap my SVT as well and I was wondering does the Fliptop kit the best match for values that can be found? I want to keep my amp as close to original as I can. Do the parts in the kit maintain the aesthetic of the amp? For example I wouldn't be too happy to replace one of the multicans with two caps and a pulltie.