MegaFlyman wrote:I clearly joined the right forum - concern for safety is right up there with technical knowledge. I do appreciate the concern regarding the high voltage and I am aware of the risks. As I am a novice at amplifiers, I do have the disipline from an BS degree in electromechanical engineering and a good amount of experience working on electronics to ensure good and safe practice. Knowledge is the key and that is why I am here. I am a DIY kind of guy and Im sure you all can appreciate the degree of satisfaction from fixing things yourself. I will drain those caps and work with one hand in my pocket.
I've attached a photo of the "data sheet" affixed to the inside of the amp. Fender thought they built an AB763. Sluckey I appreciate the post anyway.
10thTX, pretty much what I was looking for in the links. Thank you. I will read those pages in depth. However I have yet to find the AB763 schematic/layout with the electrolytics highlighted, but from what I have now seen I'm getting more confident that I can figure it out. See my other photo of my amp. I see 4 larger brown caps. The two on the right are doubled up. So I count five 25-25 and one 25-50 bias cap(which i will replace with 100 V). Have I got all of them?
One final note. I've replaced the filter caps under the sardine can on the other side. AB763 has three 20-525 caps. I replaced those three with F&T 22-500. I'm measuring 463 V. I think those are adequate. Agreed?
Thanks for the feedback. I'm looking forward to reading more.
MFM, here's my early 65' AA165 that I recapped. It had two dual 25/25 Astron and one single 25/25 Astron. Someone had installed two singles at one dual location in the early 70's.
I installed F&T caps under the doghouse, Sprague hi temp caps on the cathodes and bias locations, while replacing all the rectifier diodes as well. Also converted the AC cord to a 3 conductor and wired the fuse on the hot side on the AC mains.
TM
You do not have the required permissions to view the files attached to this post.
I've circled the caps under the chassis that usually get replaced. AES has a dual 25/25 µF @ 25 VDC if you want to use duals like the original. Pricey though.
I would replace the cap on the bias board just because some expensive parts rely on it being good. But IMO if the amp sounds good and the tremolo works I would not replace the ones on the main board just to keep it unmolested.
You do not have the required permissions to view the files attached to this post.
I have taken the old caps apart and put the new caps inside the originals. I carefully unrolled one end of the paper cover just enough to slide the can out. Then I used a small roller type pipe cutter to cut one end of the can off. Clean it up and put the replacement cap in there... A little silicone to keep it in place. Be sure to pay attention to how you insulate the positive lead exiting the can. Reassemble. If heat inside the chassis is an issue I don't recommend doing it. I don't do this to the caps that live in the pan.
This takes quite a bit more time but some people love this, being able to keep the stock look. The music store I work with buys vintage amps and we usually do this to them.
Blah, blah, blah.... Need more coffee... (Clanks coffee pots with Miles and all others drinking java)
Don't do anything you can't reverse later... Good luck!
Tony
"Education is what you're left with after you have forgotten what you have learned" - Enzo
