Ampeg V9 - for bass?

brycycle · Post by **brycycle** » Sat Nov 25, 2006 9:21 pm

thanks greg and ben.

i've actually tracked down a '73svt which is on hold for me until monday. 1080CAN shipped. all original, except for a horrid re-tolex job.

i found those same svt ads, but can't get anyone to either a) ship or b) separate the head from the cab.

hopefully this one comes through; if i can unload my ashdown and traynor on ebay.

soundmasterg · Post by **soundmasterg** » Sun Nov 26, 2006 11:49 am

One thing to be aware of with SVT's, especially vintage ones, is that if they are truly vintage with all original caps and resistors, they will need some work. At the very least you'll need to replace every filter cap in the amp, and sometimes will need new resistors and coupling caps too, or maybe a fan like I need on mine. If you do the work yourself its not too bad, but if you pay a tech, it can be some money. Take a look at this link and read up on what they did to it.

http://p210.ezboard.com/fampworkshopfrm5.showMessage?topicID=1506.topic

My SVT needs a fan, and aside from that, I've replaced two filter caps and fixed a factory miswire on the back of the mid switch. I still need to replace the other filter caps and really go through and check the resistor values and other caps, but they're hard to work on, and very involved, and I haven't had the time. It works ok now after replacing the two bad filter caps, except for the noisy fan.

brycycle · Post by **brycycle** » Sun Nov 26, 2006 12:30 pm

thanks greg. yeah, i know what i'm in for - luckily my friend (and drummer of my band) is a certified tech and has offered his time. i just have to cover the cost of the caps,etc. i'll try to assist so i learn something.

brycycle · Post by **brycycle** » Thu Nov 30, 2006 6:56 pm

got the v9 today, in fantastic all original shape! but - a power tube is out. could anyone suggest the best current production tube for the power section?

jnbass · Post by **jnbass** » Thu Nov 30, 2006 9:30 pm

reissue Tung-Sols! or SED's, EH

soundmasterg · Post by **soundmasterg** » Fri Dec 01, 2006 1:04 pm

As I said on the Amp Workshop forum, theres lots of choices, and you should replace all the power tubes at the same time, rather than just one at a time. They should also be matched too for best performance. Good choices would be the Winged C/SED 6550C or KT88, the EH KT88, the JJ KT88, or the new Tung-Sol 6550. You can get them all except the Tung-Sol from www.tubesandmore.com. Make sure to rebias the amp when you change the power tubes.

brycycle · Post by **brycycle** » Sun Dec 03, 2006 4:51 pm

i picked up a full V9 set from fliptops (winged C 6550 in the power section). thought i might as well flip them all at once and keep the magnavox preamp tubes as back-ups. i turned the amp on the other day and a minute after firing it up it went BBZZZZTTT, then shut down and won't fire back up. uh-oh. any thoughts?

soundmasterg · Post by **soundmasterg** » Sun Dec 03, 2006 6:15 pm

Hmmm...its hard to say what the problem is. It could be bad filter caps, bad screen grid resistors, bad bias supply, bas fuse......who knows. It will require someone who knows what they are doing to look at it and troubleshoot it.

If it was in front of me, I'd take all the tubes out, make sure the fuses are good, hook up a load, and turn it on and see what I find. I'd be checking for voltages in the correct places. If the filter caps are all old though, then I'd replace the caps before firing it up, since a shorted cap could cause the power transformer to go among other things.

brycycle · Post by **brycycle** » Sun Dec 03, 2006 6:33 pm

yeah, as soon as the tubes come, i'll lug it over to my tech/drummer. i'm sure he'll appreciate it (sarcasm). when you say "cause the power transformer to go", do you mean permanently damage it, requiring replacement?

jnbass · Post by **jnbass** » Sun Dec 03, 2006 10:57 pm

and THAT, is bad!

soundmasterg · Post by **soundmasterg** » Mon Dec 04, 2006 9:51 am

Yes, possibly Bryce. If a filter cap goes bad, it allows too much voltage to short to ground, so it ends up being like a dead short across the power transformer. Heat builds up inside the transformer and eventually it reaches its limits and a winding shorts internally. This can take hours, or seconds, depending on the amp and the circuit around it, and how bad the short is. That is the main reason why everyone recommends to replace old filter caps....because if they are bad, it makes more expensive stuff fail, and Murphy's law is always in play too.

If the amp is blowing fuses, even with the tubes out, and the filter caps have all been replaced, then you want to disconnect all of the secondary leads on the power transformer, make sure the fuse is good, and then fire it up. If it still blows a fuse, then it is toast. It doesn't happen super often, but it does occur often enough to stay on top of your amps and not try to use them with bad filter caps.

brycycle · Post by **brycycle** » Mon Dec 04, 2006 10:24 am

great...let's hope that it wasn't the transformer. as soon as the new tubes come in, i'll haul it over to the tech.

in the meantime i was thinking of cleaning it. as everyone always warns of the voltage running through these amps, do i run any risk of frying myself by simply cleaning it?

brycycle · Post by **brycycle** » Mon Dec 04, 2006 11:55 am

oh - and thought i'd ask: anyone know where to find a black retangle-shaped ampeg logo w/ white writing that would replace the one on the front of my v9?

jnbass · Post by **jnbass** » Mon Dec 04, 2006 3:08 pm

Antique Radio Supply, FlipTops.

soundmasterg · Post by **soundmasterg** » Tue Dec 05, 2006 9:15 am

The only risk from cleaning it is if some of the caps still have a high voltage on them and you are cleaning inside the chassis. The caps can hold a high voltage for years sometimes, so I'd be careful of that and stay away from the inside of teh amp unless you have a safe way to discharge the caps. This would be to have some test clips hooked up to a 10k resistor. One end goes to ground, and the other to the cap's positive lead. Do this on the main filter cap, and leave it on while you are working on the amp. Make sure amp is not plugged in.