fini Posted December 2, 2004 Author Share Posted December 2, 2004 binkt, That is extremely nice of you! So, you are using Mark IVs? What can you tell me about them, and have you done the mods yourself (Curcio boards, etc.)? Welcome to Ye Olde Klipsch forum! I'm not sure how to determine the value of a good transformer, though. Craig, Do you think the other transformer night be problematic? Should I try it out with a "disposable" speaker? Quote Link to comment Share on other sites More sharing options...
binkt Posted December 2, 2004 Share Posted December 2, 2004 Thanks, I have a pair of MKIVs and one of them had a fried output trans. I replaced both with EICO Stereo 70 power transformers and Curcio input boards with replacement caps copied after Joe Curcio's design. They put out wide band 30 Watts pretty honestly. I also have Mark IIIs with the Curcio treatment with which I am quite pleased but they are 60 Watts and another story. I would encourage your attempt to replace a power transformer but would caution you to be real careful as the 400+ volts provide a truly lethal shock hazard. Other than that the electronic work is achievable by anyone willing to read the Dynaco assembly manual or to follow the instructions which are supplied with Mr. Curcio's offerings. The tubes used in the Mark IVs (EL34/6CA7)provide excellent sound and can be simply wired as triodes for 15 watts. This value will drive Klipshorns to outputs satisfactory for any domestic space. The driver tube is getting a bit spendy and not so available which is why I changed the input driver boards. Enough. Quote Link to comment Share on other sites More sharing options...
Deang Posted December 3, 2004 Share Posted December 3, 2004 What causes a power transformer to fail? What about an output transformer? Quote Link to comment Share on other sites More sharing options...
ben. Posted December 3, 2004 Share Posted December 3, 2004 Dean- did you get my mail? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 3, 2004 Share Posted December 3, 2004 ---------------- On 12/3/2004 12:27:57 AM DeanG wrote: What causes a power transformer to fail? What about an output transformer? ---------------- 40 year old gear run way out of specification. Also these amps were wired with SS rectifier which raises the B+ which doesn't help matters. Craig Quote Link to comment Share on other sites More sharing options...
fini Posted December 3, 2004 Author Share Posted December 3, 2004 ---------------- On 12/3/2004 8:54:00 AM NOSValves wrote: ---------------- On 12/3/2004 12:27:57 AM DeanG wrote: What causes a power transformer to fail? What about an output transformer? ---------------- 40 year old gear run way out of specification. Also these amps were wired with SS rectifier which raises the B+ which doesn't help matters. Craig ---------------- Craig, Does that put the other PT at greater risk of failure? In other words, is the stress on the transformers cumulative, and this one's ready to go? I dunno, sounds like too much of a gamble here. I'm still leaning toward returning them. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 3, 2004 Share Posted December 3, 2004 Fini, From the looks of it yes it did experience some heat issues like I have mentioned in this thread more then once. I would also confirm the Output transformers are working properly before I would proceed. Just my 2 cents worth. Craig Quote Link to comment Share on other sites More sharing options...
fini Posted December 3, 2004 Author Share Posted December 3, 2004 I realize you've mentioned that several times, I was just wondering if repeated "heat issues" (I guess as evidenced by what looks like something oozing from the top of the transformer) made it more likely to fail, even if I were to rebuild the amp with tube rectification. OR, is it the case that as long as it doesn't blow, it should be good, as long as it's not over-stressed? I'd hate to invest a lot of time and money in a project, only to know that the heart of the amp was on its last legs. Sorry to take so much time on this. Sounds like it's all pretty much a crap-shoot anyway. I'll tell you though, Bill at K&B was able to test that PT fully in about 3 minutes. It's amazing watching someone who knows what he's doing (and has the tools at hand). Quote Link to comment Share on other sites More sharing options...
sunnysal Posted December 3, 2004 Share Posted December 3, 2004 fini, you have seen enough to pass on these IMHO. wierdly modified, wounded amps with an unknown list of problems should be passed on unless practically given away. if you are patient you can find a pair of ugly (cosmetically challenged)mkIIIs or mkIVs with all working parts for $250-350 and build from there. these are more trouble then they are worth IMHO. regards, tony Quote Link to comment Share on other sites More sharing options...
fini Posted December 3, 2004 Author Share Posted December 3, 2004 Yes, that's where I'm headed. I was thinking I'd try out the "good" one, using the pre-out on my Mac 1900 SS receiver, just for hoots. Could this in any way harm the Mac? I'll use a speaker I don't mind wasting... Quote Link to comment Share on other sites More sharing options...
fini Posted December 3, 2004 Author Share Posted December 3, 2004 Well, she's a-playin'! No hum, very clean sound! Maybe it's because both channels are being driven by the same preamp section (in the Mac 1900), but I am not hearing much difference at all between the right (SS amp) and left (MK IV) sides. I tried it out on an old Yamaha NS-5, then moved on to the Khorns. 4 ohm tap (is that correct? Sounds fine to me). So, I guess if I wanted to get deeper into this, I'd do as Craig suggests, and swap output transformers. How long should I wait, and are there any proceedures for draining the caps, etc. of lethal voltage, before getting in there? Maybe I should offer the seller $100 (I doubt he'd take $50) for the one good one, and he might throw the other in, I dunno. Quote Link to comment Share on other sites More sharing options...
fini Posted December 3, 2004 Author Share Posted December 3, 2004 I'm noticing after about 45 minutes the Mark IV has an aroma that the Mac 1900 has not... mmmm..... Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted December 3, 2004 Share Posted December 3, 2004 OK... I got it... Craig was right about the name of the place. http://www.heyboertransformers.com/index.shtml Wether you decide to take the risk of keeping them or not, it's interesting to know this place exist. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted December 3, 2004 Share Posted December 3, 2004 fini here is another amp for you to check out, A pilot 232...el84s yummy... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5735528804&fromMakeTrack=true this will probably go for less than $250 or go for this beauty, http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5735915738&fromMakeTrack=true this will go for more...but who knows...I may bid on this one...it is on my "must have beofre I die" list...the others are a pair of brook 12A, a citation II and a marantz 8B... I like these, tony Quote Link to comment Share on other sites More sharing options...
fini Posted December 3, 2004 Author Share Posted December 3, 2004 Yes, I have both those bookmarked as well! Sheltie Dave says he's got one packed and ready to ship to me (but ain't seen hide nor hair o' him...has anyone?). That gold one is a real beauty. I called the seller on these Mark IVs, explained about the dead PT. He offered to either buy them back, or give me a $50 refund (which I opted for), so it looks like I have a project on my hands! My buddy (the kicked-off-of-here-and-should-be-given-another-chance Clipped & Shorn ) has offered to show me the finer points of slinging solder (or is that flinging fodder?). So, how long does the possibility of getting a shock exist after the amp is unplugged? Do I have to wait a day, a week, or more before swapping the output transformers? And can I just be logical, noting which wires go where (I love digital cameras!), and de- and re-solder? If the good amp sounded good (it did), does that mean the OPT is good? Nothing possibly hidden? Right now, my main concern is the OPT on the "bad" amp. Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted December 3, 2004 Share Posted December 3, 2004 ---------------- On 12/3/2004 8:17:26 PM fini wrote: If the good amp sounded good (it did), does that mean the OPT is good? Nothing possibly hidden? Right now, my main concern is the OPT on the "bad" amp. ---------------- While definitively not the definitive way of testing an OPT, you can simply compare the DC resistance reading of the primary and secondary winding of both OPTs. If the suspicious one read the same that the known good one, chances are that it is OK. This is not a fool proof test and definitively fall in the quick and dirty type of methodology but it should dissipate 80% of the doubt (or 70%... or 90%... or 60%...). Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted December 3, 2004 Share Posted December 3, 2004 ---------------- On 12/3/2004 7:17:52 PM sunnysal wrote: fini here is another amp for you to check out, A pilot 232...el84s yummy... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5735528804&fromMakeTrack=true this will probably go for less than $250 or go for this beauty, http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5735915738&fromMakeTrack=true this will go for more...but who knows...I may bid on this one...it is on my "must have beofre I die" list...the others are a pair of brook 12A, a citation II and a marantz 8B... I like these, tony ---------------- The Pilot 232 is in my list too. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted December 3, 2004 Share Posted December 3, 2004 well guy that gold one looks mighty nice! I will probably bid on that one...christmas present (or at least that is what I will tell my wife)...tony Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 4, 2004 Share Posted December 4, 2004 Hi Ryan Quote Link to comment Share on other sites More sharing options...
garymd Posted December 4, 2004 Share Posted December 4, 2004 ---------------- On 12/4/2004 11:35:41 AM NOSValves wrote: Hi Ryan ---------------- LMAO. He just can't help himself (neither can you). Quote Link to comment Share on other sites More sharing options...
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