Hi all
I have my good buddies 73 PTP Superbass here. Initially it was blowing the mains fuse. I took the amp out and retubed it with a brand new quad of JJ EL34 I have on hand. The plate voltage was 512 and I set the bias accordingly. I replaced the mains fuse when I changed the tubes as well.
Ran the amp and (he uses a hot plate ok) it's 16 ohm just like the output load
I ran it loud and then the power indicator started to "dim and load" with my guitars input ok. I'd strum and you'd see the light drop and go up. (Like a visual current indicator). The output volume was "wavering" and the HT fuse then blew. I stopped at that point.
I put the proper spec SB time delay fuses in it. I think the filters might be dried up and the bias caps as well.
I realize this could be a bad PT possibly as well
The amp is 125% original. Everything. He got it from ROYAL BRIT and it looks like it came from the original owner or from a umplayed collection. It's immaculate
Has original bias caps, all original Daly filters. The dye joints are 125%. The board was never lifted
I am thinking I should replace the bias caps and the filters...
Am I correct here in my logic?
Please advise and sorry for the dumb questions
Regards
Dan
73 Superbass Issues (fuses blowing)
Moderator: VelvetGeorge
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73 Superbass Issues (fuses blowing)
MetroAmp addict!
JTM 50/45,1987's & 1986
1959 and 2203/2204 Amps
1974 amp
Can't stop building, very addictive!
JTM 50/45,1987's & 1986
1959 and 2203/2204 Amps
1974 amp
Can't stop building, very addictive!
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- Senior Member
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- Joined: Tue Oct 16, 2012 10:33 am
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- Location: Israel. Bat-Yam
Re: 73 Superbass Issues (fuses blowing)
Caps can blow the fuse. When you strum - they are discharging, but than they need to be charged again, and that's where their ESR kicks in... The rule of thumb is to change every electrolytic cap in a old amp. They die. That's it... If they die, they need to be replaced.
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Re: 73 Superbass Issues (fuses blowing)
That's exactly what I am thinking as well. I have 6 x 50/50 F&T caps here and 2x Vishhay 10 uF bias caps here
I've already started to take apart the amp cap by cap and I want to get it clean as possible.
I've redid some jumpers on the 4 caps and dyed the joints
I just want it 110% clean.
I am going to do a full valve change afterwards and bias it to 70%
Thank you for your advice
When the HT fuse popped I realized that's it and it's going to have to need some SERIOUS SURGERY!
I've already started to take apart the amp cap by cap and I want to get it clean as possible.
I've redid some jumpers on the 4 caps and dyed the joints
I just want it 110% clean.
I am going to do a full valve change afterwards and bias it to 70%
Thank you for your advice
When the HT fuse popped I realized that's it and it's going to have to need some SERIOUS SURGERY!
MetroAmp addict!
JTM 50/45,1987's & 1986
1959 and 2203/2204 Amps
1974 amp
Can't stop building, very addictive!
JTM 50/45,1987's & 1986
1959 and 2203/2204 Amps
1974 amp
Can't stop building, very addictive!
-
- New Member
- Posts: 37
- Joined: Fri Dec 19, 2014 11:34 am
- Just the numbers in order: 13492
Re: 73 Superbass Issues (fuses blowing)
Replaced 6 x F&T 50/50 and 2 x Vishhay 10 uF bias caps and did a full revalve
Set the bias at 33 and played it and it's fixed!!
Thanks for your help!
Dan
Set the bias at 33 and played it and it's fixed!!
Thanks for your help!
Dan
MetroAmp addict!
JTM 50/45,1987's & 1986
1959 and 2203/2204 Amps
1974 amp
Can't stop building, very addictive!
JTM 50/45,1987's & 1986
1959 and 2203/2204 Amps
1974 amp
Can't stop building, very addictive!
-
- Senior Member
- Posts: 413
- Joined: Tue Oct 16, 2012 10:33 am
- Just the numbers in order: 13492
- Location: Israel. Bat-Yam
Re: 73 Superbass Issues (fuses blowing)
No problem! I'm glad that it helped. Rock on!