MattB

yeah I saw those. I think I looked a while back and their largest was just a touch short. I'll have to re-measure the existing one when I get back from the track this weekend. many appreciates!

Many thanks, Bob! This one has a round belt- looks just like a vary long O-ring with about 2.5mm thickness. I searched amazon for quite a while and only found flat bands in that size. I'll keep digging on the sites you linked.

I've heard good things about the CSS kits. I built a set of bookshelves with some HiVi Research / Swans woofers and some JM Lab tweeters. I've been very happy with them for ~20yrs and they make up my office/ PC setup and get used several hours a day when I'm at home. HiVi sells a 3-way flat-pack kit that is very well reviewed and there are a number of crossover mods that improve it even more. They're sold in various places including Amazon: https://www.amazon.com/gp/product/B09XGYJFRQ/ current price is $365, but I've seen it go on sale as low as $329 if you watch. (There's a open box / returned one for $311 right now too) I wanted to build a set for the kid's room, but was gifted a set of Triangle floorstanders from a neighbor so I didn't bother spending more money.

Tagging onto this thread for somewhat relevant question... Is there a good place to order belts by size? I have a VPI turntable and the belts are $45 each direct from VPI. I can't imagine these are anything super duper esoteric, but they sure do like to charge for them.

Welcome to 1998 with my 4x CD-ROM and Winamp!!! (It really whips the Llama's ass!) I spent weeks ripping my entire CD collection to mp3 and then archiving on Zip drive once my PCs 320mb hard drive was full. Hmm I wonder if I still have that old hard drive. My wife donated that whole CD collection years ago and mayne I still have it all archived on disc somewhere.. the. Again I'd have to find a PC with a cd/DVD rom and an old SATA drive connection...

Welcome! How will it sound compared to new condition in 1992? A recapped one should sound exactly the same. How will a restored version compare to a unrestored 1992 original? There's always the question whether the caps have deteriorated enough to the point they affect the sound. You won't know until you replace them. pulling them from the circuit and testing on a meter is required to find out, and by that point you might as well just replace them. The good thing- as mentioned above- is the C-9 is easy enough to work on and the parts count is small. it's not like you are trying to recap a multi channel receiver with a gazillion inputs. Grab the soldering iron and have some fun.

I have a Galaxy S9 and within the Wiim app it includes all the RoomFit analyzer stuff. It seems to do the job and the resulting sweep response curves pass the smell test (I have weak low end and overblown highs, and the room response curves show the same)... However, I do not trust EQing my room to the >5yr old Chinesium microphone. I have been contemplating how to make this better--- can I buy an external USB mic like the miniDSP UMIK-1 and connect it to my phone, or do I have to use an external program like REW on my PC and then I can somehow transfer the file to the Wiim? I do note that when I just do the full auto-correct thing, it drops 4-8kHz by roughly 8-10dB and then everything sounds quite muffled. I adjusted that curve to cut out about 3-4dB and it quite improved. however, cymbals no longer sounded like cymbals. they were there but they weren't there. I removed all correction and, while very bright, the cymbals sounded like cymbals again. Is this poor quality EQ that jacks with phasing or overly jacks up the signal, did I adjust too far (again with a cheap cellphone mic, I don't trust any measurements), or is there something else afoot? In any case, the RoomFit stuff is there on my old Android. It works but I'm not convinced it works well.

Master of Puppets just streamed through on Spotify. I get funny looks from my coworkers when headbanging in the office. 😁

Welcome! Shortly before I found this site, I purchased a M1.5t rebuild kit from the same vendor. while all of the parts inside were quality brands, the instructions were somewhat vague and there was no list of any oddities/ updates to the design. i.e. "some versions of M1.5t had a 2.2uF cap in location C-xx, but later versions have a 10uF. this kit is shipped with a 10uF" so I had a small handful of capacitors left over and were missing others. fortunately I had a few spares in my stash from other recent projects, but I did have to buy a couple non-polar caps from digikey and wait a week to get it. There were also baggies of small signal PNP and NPN transistors and I couldn't read the part numbers. they are not listed in the instructions other than being provided "just in case you need them". that sounds wonderful! While buying singles from a place like digikey can be cumbersome, I highly recommend doing the research and digging up the parts yourself so you know what you're getting. also consider the "BillD mod" if you do decide to take on the C-1 yourself. I haven't done it yet, but planning for it as a winter project.

Howdy! What part of TX? I'm just south of Houston..

Thanks! I hoped my escapades would maybe help someone else and provide some nifty photos that not all people are willing to do.. I have no problems ripping into a project and doing a complete teardown that most people just say "send it off to a pro". I'm too impatient for that and would rather spend two weekends screwing it up myself instead of just paying a couple hundred bucks to a professional. This little thermal camera is very handy- troubleshooting is pretty much why I bought this thing. it's not a very high end camera- just one of those little $100 strap-ons for my phone, but it's great to search for faults in electronics or diagnosing a misfire on the race car (just look for which header tube is different than all the others!) I also diagnosed some bad panels on a solar array. Nifty lesson there- warm spots on a solar panel are where they aren't producing energy! The panels are cooler because they're converting the solar energy to electrical and shipping it down a wire. the places there the panel isn't converting light into electricity, it converts the light to heat and is thus warmer. It's a great cheat playing hide and seek with the kids since they leave tiny warm footprints in the carpet for a couple minutes!

Measurement is using a Klein clamp-on style amp meter around the 120VAC line wire. Bias is measured concurrently using a Fluke multimeter. Its no NIST calibrated unit, but I would think it's close enough for gubmint work- not off by factor of 2! ....Aaaaaand I just did a little digging online and this model doesn't seem to be well regarded on the accuracy front. Sooo, now I'm doubting the measurements just as you are! Maybe I'll hook the Fluke up in-line and take a proper measurement. That will also tell me whether I can trust the Klein or not in the future... At least the good news is that with this bias setting, the transformer only has minimal hum and doesn't even get warm to the touch at idle, whereas it stayed quite warm before. Yes, these tests were only for a short time- about 15-20sec since these things don't have a massive heat sink and aren't intended for long term brute force. Bob did a good job of reducing materials to just what was necessary to make music, which is very peaky by nature. I did turn it up once with no load until clipping and the protection circuit kicked in and reduced the gain (per the service manual). For load testing, I stopped turning the volume knob as soon as the "0dB" light came on and didn't push it into clipping. Now for some cheap thermal camera fun.. For some reason the browser/ forum keeps showing the photos rotated vs. what's on my PC. I've rotated them several times to try and fix the formatting, but they are always the wrong orientation! This was very shortly after the load test- inside the chassis is glowing well, but the power resistors were really putting out some heat!

Wife and kids were out of the house tonight so I had a chance to set up shop and go through biasing again. across both emitters, I was seeing almost 9mV and idle current of 1.8A. Lots of wasted heat! After turning bias back down to 3.4-3.5mV, idle current is now ~850mA. No further improvement if I reduced to minimum, so I guess that's that? I cobbled together a little more stuff and did a short test of 1kHz full power into some 5ohm power resistors. 54.5V RMS into 5ohms = 594W. There's a bit more room in there but I couldn't see the waveform well on my little scope so I couldn't tell where the clipping began and I didn't want to leave it at full power for long- these chassis just don't have much of a heat sink and was heating up quickly! I put the cover back on and let it cool down while mounting it back in the rack. After playing some low level signals for a while, the faceplate of the chassis is now idling at ~82F while my M1.0t is at 79F just below it. This makes me feel MUCH better as previously it was idling at >120F. I also took a few thermal images for fun while I had the cover off. It's interesting which little resistor bundles on each board are toasty warm while others have nothing. Will post those tomorrow once I transfer off my phone.

Seasoned? yes. Pro? no!

Hi all, many thanks for the welcome and the pointers. There have been several replies, so I'll try to do it without making a 14 page reply. - Will revisit the biasing based on @timmyjim comments. I believe you are right on checking bias across both emitters. When I first powered up the amp, the bias was at about 1-2mV across R87 on both channels. Doubling that reading to account for both emitters would put me in the 3-4mV range which matches the PM1.5 and your recommendation. Given how much handling I had done of the amp cards while they were out of the chassis, I assumed I bumped the pots on both. I blindly did what the manual said believing whoever wrote the manual was the expert! I downloaded the PM1.5 manual and diagrams off the manual repository last night. the Member Diagram pdf is awesome! And yes clipping to the emitter pins is way easier than grabbing that lower leg of R49/R87. I clipped my lead to the Q5 emitter and the top leg of the resistor. I wasn't the first in there either as the insulation on the resistor leg had been picked away for access. I also do not remember this amp running warm in the past, but again it's been sitting for easily 10 years- I considered it a win the thing didn't blow a breaker or catch fire when I powered it up! - @Rob, unfortunately no 10x probe on hand, but I'm ordering one today. My oscilloscope is a little handheld $20 junklet I bought on Amazon to commission some outdoor siren arrays for work, and it only came with a BNC to alligator clip connector. It worked for what I needed at the time. - As for the amp sounding "dry", I don't insinuate that it sounds weak, bad, or lifeless at all, it just doesn't have the warmth that the M1.0t has. Maybe the highs are a bit exaggerated compared to the M1.0t? I didn't listen to it very long or do a real A/B test with same material, I was just plugging in cables and ran it through a couple songs. I did replace C35 - the 0.33uF cap right at each channel's inputs. as the signal goes through it before anything else, I expect that cap to be essential to the sound. no idea what brand it was- it's a mylar or polypropylene ~250V cap I found in my surplus pile after breaking one of the leads off the original 'red' ones glued to the board and corroding around the legs. And now for a few pics- I didn't know you could just drag and drop photos in line - I haven't done forum stuff in years! Before: You can see how dirty the inside was and all the sticky buildup on the traces- hard to get clean measurements and good solder joints when everything is coated and smells like an ashtray when you heat it up! You can also see the random 2200uF cap glued to the original 50/80 caps- there's a 6800uF on the other side! This poor unbalanced amplifier! In the middle of the cleanup and reassembly work: (I replaced the mica insulators on the bottom with some kapton tape and cleaned/ replaced all of the thermal paste while testing the output transistors. No more globs of white messy goo! And back together: Another minor mod was to replace the 'lamp cord' power cable with a fused C14 socket and power switch. Back together and running for a little bit! Rest of the System specs: Pioneer AVR 7.1 receiver to run it all (forget the model #, but it's irrelevant) Sony SACD player (yeah, I bought into it many years ago!) M1.0t and M1.5t to run the JBL L7s in a biamp configuration. SurgeX power sequencer Velodyne HGS-18 sub. A freebie from my neighbor cause it had an annoying 60hz hum. replaced the caps in the audio circuit and voila! Some sort of in-wall JBLs for center and surround duties, driven off the receiver's internal amp. Next upgrade: beefier 120VAC mains cabling with multiple circuits since this whole mess is capable of about roughly 3000W RMS / 5000w dynamic power! now will I ever use it in a 16x20ft room? probably not more than a few seconds.... Many appreciates for the warm welcome and advice!