btoth76 Posted October 29, 2014 Posted October 29, 2014 Hello! Some of You are expert amp builders. I have a (couple of) question(s) for You. I am about to rebuild my late 60s Regent 30H all-tube amp (well my Dad will do it). It will be a complete restoration, no old parts will be left in it (I don't want any weak points left in it). My question is what parts would You recommend? I have no clue which resistor/capacitor brand or type is a quality one, which is not. What to look for to judge a component quality-wise? How would You start such a rebuild process? Can You recommend me component sources (in Europe, if possible). Basically, I am interested about everything You can add to this subject. Thank You in advance! The amp in question: Cheers... Bence
capmaster Posted October 29, 2014 Posted October 29, 2014 Hello Bence, if it ain't broke, don't fix it! In case you insist on proceeding your way, it will depend on specifications like component values, wiring and mounting. I think there are not so many sources offering electrolytic capacitors handling 450 V DC (500 V types were never made in Europe) matching the screw hole diameter. I guess they have a plastic thread and a matching plastic nut which were common for decades. Also consider that all the parts will have to bear the given operating temperatures. Resistors with overrated dissipation are a good idea in my opinion. Power resistors should not be a problem on principal. One will have to decide about going modern and linear using metal film resistors, or vintage with wire-wound resistors and their parasitic inductance, although this would not do that much to tone. Anyway, I would use "vintage" solder containing 40% lead, in particular because of components and soldering temperatures. RoHS compliant wires and tags can easily be soldered with lead but not the other way round. I'm in doubt if there are valve/tube sockets available matching your unit's requirements AND RoHS rules, so "vintage" solder will be the appropriate solution. Do you already have a parts list allowing for research?
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 Hello Capmaster. The thing is: this amp is functioning, but it is unreliable. On monthly basis, I am taking it back to Dad for a repair (30 mile drive). It has been rebuilt by Him, but His approach was to not to replace a component if it works (Well, don't fix it, if it ain't broke - it is His philosophy too). But the result of this, that the remaining old parts go dead one by one. So, I am tired and want all the old components out of it, and build it up with the best possible parts at once. The other reason I started this thread, is a debate between me and my father. He wants to order parts from China. They are definitely much-much cheaper, but there must be a realistic reason why a cap costs 5 Euros here - 5 cents in China. He says it is OK... but I want to be sure this time. Cheers... Bence
capmaster Posted October 29, 2014 Posted October 29, 2014 Reliability would be my main concern, too. Rereading your first post made me wonder about the strict "no old parts" attitude. Is anything wrong with the transformers? Replacing them could become a huge availability problem.
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 Reliability would be my main concern, too. Rereading your first post made me wonder about the strict "no old parts" attitude. Is anything wrong with the transformers? Replacing them could become a huge availability problem. No, I don't think anything is wrong with them, and I have rewinding shop nearby... Usually, what happens is, that it starts to hiss, crack... then I know it's time to struggle it into the car with it's 35 kilograms and take it for a ride... Tubes will be replaced, sockets (plastics for ceramics), all caps, resistors, and the pots. Cheers... Bence
L5Larry Posted October 29, 2014 Posted October 29, 2014 Although in the "States", this company specializes in amp repair/rebuild parts. I have done business with them in the past. https://www.tubesandmore.com/
capmaster Posted October 29, 2014 Posted October 29, 2014 No, I don't think anything is wrong with them, and I have rewinding shop nearby... Usually, what happens is, that it starts to hiss, crack... then I know it's time to struggle it into the car with it's 35 kilograms and take it for a ride... Tubes will be replaced, sockets (plastics for ceramics), all caps, resistors, and the pots. Cheers... Bence Sounds like a good idea to me. In particular I'm with you when about valve/tube sockets. During the 1980s I swapped plastics for ceramics in several amps of pals. EDIT: It is recommendable using screws and nuts for mounting ceramic sockets, not rivets as they might break them. But I guess your father will already know... ;)
Guest Farnsbarns Posted October 29, 2014 Posted October 29, 2014 No, I don't think anything is wrong with them, and I have rewinding shop nearby... Usually, what happens is, that it starts to hiss, crack... then I know it's time to struggle it into the car with it's 35 kilograms and take it for a ride... Tubes will be replaced, sockets (plastics for ceramics), all caps, resistors, and the pots. Cheers... Bence I'd stick with ceramic sockets. A hiss is most likely due to dry joints in solder. I wouldn't think twice about it Chinese resistors,a resistor is a resistor is a resistor. Caps yes, buy Mallory if you can.
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 I'd stick with ceramic sockets. A hiss is most likely due to dry joints in solder. I wouldn't think twice about it Chinese resistors,a resistor is a resistor is a resistor. Caps yes, buy Mallory if you can. Yes, sorry ceramics instead of plastics. A mistyping... So, You would recommend Mallory caps. Thank You! Best wishes... Bence
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 Although in the "States", this company specializes in amp repair/rebuild parts. I have done business with them in the past. https://www.tubesandmore.com/ Thank You! Lot's of fine stuff there. :) Best wishes... Bence
capmaster Posted October 29, 2014 Posted October 29, 2014 Yes, sorry ceramics instead of plastics. A mistyping... ... There has to be a peculiar resonance between us. By reading it wrong I got it right! [lol]
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 Hello Capmaster! Yes, it was such an evident thing...it could only have been a mistyping. :) The other interesting things is: No matter what we do, these amps do hum... one or two of them more, this one is not that bad, however it would be great if it was noiseless. Anything You can think of that is missing from such an old amp that is present in a modern amp regarding this issue? I am using a Belkin adapter, and my house has been completely rewired with new ground post and such. Thanks again. Bence
capmaster Posted October 29, 2014 Posted October 29, 2014 Hello Capmaster! Yes, it was such an evident thing...it could only have been a mistyping. :) The other interesting things is: No matter what we do, these amps do hum... one or two of them more, this one is not that bad, however it would be great if it was noiseless. Anything You can think of that is missing from such an old amp that is present in a modern amp regarding this issue? I am using a Belkin adapter, and my house has been completely rewired with new ground post and such. Thanks again. Bence Hum from an amp itself, i. e. no input hum, may come from weak filter capacitors, and in case of a push/pull output stage from imbalanced power valve/tube bias or lack of coil balance within the output transformer. Another point is the ground wiring. Star grounding is always a good idea within valve/tube amps.
surfpup Posted October 29, 2014 Posted October 29, 2014 One problem with older amps like that can be the cap cans. Often there are three or four different capacitors inside of there and you cannot find replacement "cans". As a result you may have to do some fancy wiring to replace the bad cans (if they are bad). Hopefully you have a schematic. Not sure if that was as clear as it should be. English is my first language.
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 One problem with older amps like that can be the cap cans. Often there are three or four different capacitors inside of there and you cannot find replacement "cans". As a result you may have to do some fancy wiring to replace the bad cans (if they are bad). Hopefully you have a schematic. Not sure if that was as clear as it should be. English is my first language. Thank You, Surfpup! To me it is completely unclear, regardless of the language...I know nothing about electronics. :D If I am correct, You are talking about the big, electrolytic capacitors in the power section(?) I collect, and forward all posts to Dad. He used to work as an electro-technician in His youth. Hopefully, He will understand. :) Best wishes... Bence
btoth76 Posted October 29, 2014 Author Posted October 29, 2014 What about wires? Is there any important aspects? Bence
Guest Farnsbarns Posted October 29, 2014 Posted October 29, 2014 The wiring it was made with would almost certainly have a meaningful capacitance and the circuit would have been designed around that. The chances are the amp will sound quite different if you rebuild it. Just be aware of that.
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