If you would post a pic of the underside of the amplifier and a name we would be able to help even more. Last edited: Feb 12, Already mentioned- replace electrolytic type caps. Sonically, coupling caps have the largest effect. Rebuilding for others? Forget boutique caps. Biggest bang for the dollar are Russian K40Y-9 coupling caps. And, I rebuilt newly rebuilt from others with that other cap.
Some say no difference in various coupling caps. BTW- do not change the value of feedback caps with out using lab equipment. My 2 cents On the schematic I can see that the filter caps are significantly larger value but I don't know how to read all of a schematic yet to distinguish the coupling or decoupling. I'm taking electronics classes now and expect to learn eventually but of course I'm anxious to "do" something instead of reading DC theory.
I'm trying to figure out how to post a pic of the Eico hf30 and will as soon as I do. Power supply and filter capacitors are the same in this case. The caps 'filter' out the AC component in the DC power supply to a large degree. I would look up coupling capacitors on a Google search or in an electronics educational book.
It would be rather wordy here to explain where coupling capacitors would be located without explaining how an audio amplifier performs plus reading schematics. Interesting how some or most of us do not even need a schematic to troubleshoot or rebuild an amplifier. I certainly needed guidance early on. After a while us techs memorizes the tube pins on a socket for most tube types and the associated components fall into place without thinking about it.
Messages: FidgetMaster , Feb 12, Pics of Eico hf30 Here's the pics of the Eico hf30 chassis top and bottom. Correction: In earlier thread, I stated that I purchased a.
Perkinsman , Feb 13, Nice looking amp. Would sure be nice to own two of those. If you are going to make a full recap here's what you should do. C7A-D are the filter capacitors. They are essentially two 20uF v and two 10uF v. C8 is a Y2 or X2 capacitor. This means it is tested to work on a AC and if you happen to touch it, it won't kill you.
C9, C3, C6 are coupling caps and should be replaced with polypropylene. C1, C4 can be replaced with whatever suits you but using polypropylene will be the best choice. C5 and C2 are electrolytic. It would be wise to choose a high temp cap here. While you're at it, measuring all of the resistors is not a bad idea. Correct schematic for my model Eico hf30 Thanks for the continuing help.
I just found out that there were multiple versions of the hf30 and my initial schematic was not the model I own. Here is my model. Sorry but I guess I have to start again by asking what each cap is and what I should replace them with. Edit Note: sorry, the image is blank, I'll follow up with a good pic of my schematic model. I thought that f. And I have a CRT monitor, on which I can turn the brightness down quite a lot for night viewing, so that f.
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Find More Posts by shovenose. Posting Rules. Make sure the output selector is nice and tight. I also lube the pots and jack contacts with Deoxit Gold dropper - not spray. Joined: Dec 7, Messages: 17, Likes Received: 17, Last edited: Nov 19, Thanks for all advice I will order filter caps and bias caps just to be sure I have them in case they need replacement.
And will go through it thoroughly and clean it too. I built a JTM45 clone last spring which I have been using in my band, but selling that one to afford this vintage monster So I have some experience with this type of amp.
I have a bias probe too. The bias caps is the 2 in the red circle right? There is a last electrolytic cap near the input stage green circle , is that one also subject for replacement? I will order 3 of this and 2 of this And hope this machine pairs well with my 74 Les Paul deluxe Thanks again and I will post follow ups later!
The small cathode bypass caps see no real voltage so are very unstressed and virtually never fail. Aim for the best quality filter caps you can. You can get 2x10uf at v and those would be acceptable. The beast is home. Someone has been poking around here that is for sure.
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