spritzer Posted September 18, 2009 Report Posted September 18, 2009 This is the story of a very sick little Firstwatt F5 that needs some TLC. This is hopefully the last chapter in a rather sad story involving our Scottish Lord of Drink. Dough bought it from some scammer on DIYAudio which not only botched every facotr of building the amp but couldn't even be bothered to ship it properly. To fast forward a bit I had expressed my intention to build an F5 here and Doug offered to send me this amp to do with as I pleased. I took this a good chance to tinker with an F5 and help a friend out since this amp will be returned to Scotland in fully working condition later on. Now onto what awaited me in that 13kg box from Scotland. Parts of this build have quite a lot in common with the SinglePower craftsmanship so some deja vu as I started to dissemble it. The amp is built into a Hi-fi2000 3U chassis which is really too small for this amp (Class A baby!!!). Here is the bottom panel of the amp which housed the transformer, rectifiers and the PSU board. As you can see the bottom panel is badly damaged since it was way too thin to hold that massive transformer in place. To make matters even worse the builder neglected to put any washers on the bolt even fully tighten it. I rotated one of the rectifiers for the picture and you can see that there was no thermal paste applied, straight out of the SP rule book. The guy was obviously using a drill for the first time in his life since he didn't clean off the debris which gathers around the holes or even hold it tightly. Now there were no hookup wires in the box at all (apart from the transformer leads) and I'm fairly sure that there is something missing from the amp boards. It's the magical F5 with no output devices!!! Also, who needs to bond those input fets together for better thermal stability... It's clear that this guy has never heard of masking tape or that spacing output terminals a couple of inches apart is a good idea without an extensive protection circuit in place. It's quite clear that this guy wasn't suffering from OCD given how these PSB's were stuffed. Look at the soldering in the bottom pic... wow... just wow... Now the first job is to make sure this idiot managed to put the right parts where they are supposed to go and then redo every solder joint. Then I have to see what parts I need to get it up and running and figure out how to salvage that bottom panel and make it strong enough to support the transformer. I'm thinking about a thick aluminum plate on top of the steel and placing a support toot directly underneath it. That should carry the weight but it will need some more bracing to be sure.
swt61 Posted September 18, 2009 Report Posted September 18, 2009 Wow! Just wow! As for the good news...This makes me feel really good about my first ever amp build (also F5).
digger945 Posted September 18, 2009 Report Posted September 18, 2009 Perhaps the fella missed a couple of days medication, or maybe took double doses:eek: I have been eyeing this(and many other) pass amps lately. It will be fun to watch you repair it and then to know what you think of how it sounds. I agree with your assessment of the transformer mounting. If I were going to ship it anywhere I would want the transformer mount to be as sturdy as possible. Let me know if I can help with parts or mounting brackets in any way.
luvdunhill Posted September 18, 2009 Report Posted September 18, 2009 I'd recommend using the FQA19N20C / FQA12P20 devices over IRFP240 / IRFP9240 if we're talking about the easily available choices. You're also missing the thermistors. If possible, mount the bridges on the heat sinks themselves, they'll get warm.
Duggeh Posted September 18, 2009 Report Posted September 18, 2009 Lesson learned. IF the price looks too good to be true. It's probably too good to be true. That guy was an unconditional fuckwit bullshitting scam artist and it astonishes me that he wasn't banned from DIYAudio for this plus his other multitudinous rip offs. He's on HF too. Birgir can bake cakes in the chassis and use the trafo as a curling stone for all I care. I was glad not to have to look at the fucker anymore. Just seeing it made me angry.
spritzer Posted September 18, 2009 Author Report Posted September 18, 2009 (edited) Small update: I've redone every solder joint, fixed the majority of the large resistors and removed the messed up ZTX450. I've also cleaned up the front panel (had a lot of tape residue on it) so it's ready for drilling in the morning. Moar leds!!! There is a small mark next to the thermistor so it's the perfect location for one of the leds, the other a mirror image. I have been eyeing this(and many other) pass amps lately. It will be fun to watch you repair it and then to know what you think of how it sounds. I have high hopes for this one. I'm thinking about building a Dynalo preamp (S22 psu) with a RK50 volume control and a dual mono F5. I agree with your assessment of the transformer mounting. If I were going to ship it anywhere I would want the transformer mount to be as sturdy as possible. At least tighten it with some washers to distribute the load. The bottom panel is only fixed with 4 screws and there is nothing fixing it in place to the front panel or even supporting it... Let me know if I can help with parts or mounting brackets in any way. Thanks. I'd recommend using the FQA19N20C / FQA12P20 devices over IRFP240 / IRFP9240 if we're talking about the easily available choices. You're also missing the thermistors. If possible, mount the bridges on the heat sinks themselves, they'll get warm. The bridges are going on the heatsinks or a thick aluminum platform that I'll mount underneath the transformer. Hell I'll perhaps just replace the bottom with a 5-6mm sheet of aluminum. I just checked and I can get the IRF's locally but not cheap at roughly 10$. This shop had a nice stash of SJ109's a lot things may lurk there so are there any other obscure parts that may work? I do need the thermistors and a single ZTX450 since the builder had mounted it the wrong way and ehhh cut the leads and then soldered it flat to the board at a 90 Edited September 18, 2009 by spritzer
Duggeh Posted September 18, 2009 Report Posted September 18, 2009 So is a 909, which has 140 watts... IF I get the 63. Expect to see a 909. And the JH13 be buggered.
Duggeh Posted September 18, 2009 Report Posted September 18, 2009 Argh, just got an email in from the guy about the buy detailing what-was-what, followed minutes later in my inbox time by "but they've sold". Hatin it.
spritzer Posted September 18, 2009 Author Report Posted September 18, 2009 That sucks... Well it's not like they are rare though. One question for the group, does anybody have any data on this transformer: Avel Lindberg 2002 LTD. (aka the Uk branch) model: AT CA6776/1 Google gives me nothing... \
John Buchanan Posted September 18, 2009 Report Posted September 18, 2009 Duggeh, you're gonna love that ESL63 - my father has a pair and they are superb. I have the 989s and they are magic.
Duggeh Posted September 18, 2009 Report Posted September 18, 2009 I'll love one eventually, just not that one. It was the price that was magic, once id confirmed they really were in good nick. The seller has just moved onto a full 24 bit Meridian system with their Active DSP Speakers. So the -63 was going to balance the books on that one. Nice guy I'd have liked to meet him when I went to see them. I'll just tell myself that they're not best suited as desktop speakers anyway....
luvdunhill Posted September 18, 2009 Report Posted September 18, 2009 Pfffft.... you'll need an amp for those ESL63's and this one is stable into 2ohm.
Duggeh Posted September 18, 2009 Report Posted September 18, 2009 That sucks... Well it's not like they are rare though. One question for the group, does anybody have any data on this transformer: Avel Lindberg 2002 LTD. (aka the Uk branch) model: AT CA6776/1 Google gives me nothing... \ I was sure I looked it up at the time I bought it and found something. However googling now, leaves me dry too. Sellerfuckface told me it was oversized for the amp, but then we know he was the last word in competance truth and honesty.
cetoole Posted September 18, 2009 Report Posted September 18, 2009 I'd recommend using the FQA19N20C / FQA12P20 devices over IRFP240 / IRFP9240 if we're talking about the easily available choices. You're also missing the thermistors. If possible, mount the bridges on the heat sinks themselves, they'll get warm. Unfortunately, the Fairchild parts are all NRND now, I believe. Mouser and digikey dont seem to have anything in the way of stock either.
spritzer Posted September 18, 2009 Author Report Posted September 18, 2009 Nice!!! It will be nice to finally wake up the old Tannoy R2's. I was sure I looked it up at the time I bought it and found something. However googling now, leaves me dry too. Sellerfuckface told me it was oversized for the amp, but then we know he was the last word in competance truth and honesty. I'm pretty sure that this is a 330VA transformer and it is easy enough to see which are the primary and secondary windings but I really need the phase as well... \ Unfortunately, the Fairchild parts are all NRND now, I believe. Mouser and digikey dont seem to have anything in the way of stock either. Looks like Doug will get IRF's in this amp then.
digger945 Posted September 18, 2009 Report Posted September 18, 2009 Tech DIY Company Store Don't all Avel toroids use one standard wiring scheme ?
n_maher Posted September 19, 2009 Report Posted September 19, 2009 He's on HF too. User name, right now.
Nebby Posted September 19, 2009 Report Posted September 19, 2009 I'm amazed that the builder thought putting a F5 into that chassis was a good idea to begin with....
spritzer Posted September 19, 2009 Author Report Posted September 19, 2009 Over on DIYAudio they've recommended the 4U version of this as the bare minimum but 5U being better. I'll probably decrease the bias a bit but adding some mass might help matters...
kevin gilmore Posted September 19, 2009 Report Posted September 19, 2009 you think that is some bad soldering, look at this one, the lastest SP disaster http://gilmore.chem.northwestern.edu/raffy3.jpg Not even sure how you get cold solder blobs like that.
Duggeh Posted September 19, 2009 Report Posted September 19, 2009 Nice!!! It will be nice to finally wake up the old Tannoy R2's. I'm pretty sure that this is a 330VA transformer and it is easy enough to see which are the primary and secondary windings but I really need the phase as well... \ Looks like Doug will get IRF's in this amp then. Doug won't get bugger all in this amp. The amp is yours. I'm going Quad 909, it's just a matter of when. I'll trade you in the return against building me a T2 or an olive loaf, or a trip to the penis museum or something. Just don't even think about return involvement. User name, right now. 2 secs.... Head-Fi: Covering Headphones, Earphones and Portable Audio - View Profile: rhys h His Feedback thread on HF.
Duggeh Posted September 19, 2009 Report Posted September 19, 2009 That takes skill... My first soldering joints looked like that, and I had an OLD iron at the time which was down to the copper core and needed the rust scraped off of it every minute or so as it formed. I was literally soldering with a nail you find on the beach. I wish a had a photo of it.
n_maher Posted September 19, 2009 Report Posted September 19, 2009 Head-Fi: Covering Headphones, Earphones and Portable Audio - View Profile: rhys h His Feedback thread on HF. He gone.
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