Hello,
Does any one has the schematics for the A100 model please?
Thank you.
Hello,
Does any one has the schematics for the A100 model please?
Thank you.
Matt - could be a silly and/or obvious answer here but I'm a relative newbie so I'm going to ask...
If that large 10W resistor did become unsoldered, would the fan only just spin on high (very high in fact) when the amp is turned on? Because that's what's happening on an A400 I have.
Thanks?
Unfortunately no, when these big ballast resistors become unsoldered the fans stop and *ONLY* spin when the protection circuits kick in. I almost always put 15 or 20 watt units in (they are usually bigger and can expel heat better) to keep board temps down. I would say this is the biggest failure point with the mosfet amps with fans. I have repaired a bunch of these units and have seen some pretty interesting *fixes* that people have devised when the fans stop running on low.
The primary caps appear to test fine, I tested with a Blue ESR meter, both caps tested within range.
Thinking I should check rail voltages next in chasing down this fan that runs only on high.
Do you happen to have the schematic for the SOUNDCRAFTSMAN FOUR amplifier ?
I cant find, I am especially interested in the adjustment of the four trimmers.
Hi, I'm new to the board, found this site looking for info on a SC PCR800 that has an issue with high rail voltage on one channel. I hate to see a thread with this much info in it die off.
Should I start a new thread with my amp issues, or piggyback onto this thread? Is there a tech in here that is familiar with the PCR800 PS circuits, namely the regulator? Thanks for a great site.
Kevin
You might try a new thread. It’s really a crapshoot as to who may notice a given thread and respond to it.
FWIW: I used to have a pile of those compact amps. Soundcraftsmen made a number of variations. I’m not sure what the differences were.
Widget
Interesting, I believe I had a pair of PM860s and a single PM840 in a home theater set up. I used one channel of each for the HF and the other channel for the woofer on three identical two-way speakers performing LCR duty. I never noticed a difference between the two amp designs.
Widget
The specs are the same on those 3 amplifiers down to 2 ohms stereo, 4 ohms mono. Performance wise there is no noticeable difference unless the load drops below that limit which then the PM860 (S860) will handle it with less stress due to its higher output current. That's why it was marketed as part of the professional line. I have run all those models in 4 ohms mono, 2 ohms stereo at consistent loud levels with no issues. http://www.hifi-classic.net/review/s...cr800-498.html http://ampslab.com/blog/2018/09/30/s...ftsmen-pcr800/
Shot in the dark: Anyone here had experience removing the volume knob from a Pro Control Four? Not sure there's any way to clean the pot but one of mine is having an intermittent problem with drop-out and distortion in one channel. I know it's related to the volume control since I bumped the knob and the channel went silent. It's been a good companion for many years, so much that I purchased a spare unit which I'm now using. I'd like to try to fix the other one. Getting the pot out of the circuit board looks simple, once the knob is removed. I just don't want to force it until someone reassures me that's all it takes to remove it.
Thanks.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
Every Soundcraftsmen unit I’ve ever owned had the knobs held on by force, nothing else. Usually it’s been a typical round shaft with a flat side to aid in alignment.
Those units are getting old, so the knobs may become brittle and contract slightly around the shaft with age, which kind of melds the metal stay to the shaft. I bought one unit where the knob had cracked and fallen off when the previous owner attempted to Incredible Hulk the thing off. I had to remove by various means the plastic/metal receptacle left on the shaft without demolishing the shaft and pot (or burning it up).
I got an acceptable replacement for under a buck which pressure fit the shaft nicely at Torrance Electronics near the Del Amo mall in Torrance CA. That was over 20 years ago, so accept this anecdote at face value and at your own risk.
N.B., I’ve had far more experience with the small, rectangular push buttons on Soundcfaftsmen gear NOT keeping their grip and falling off willy-nilly without any provocation whatsoever.
Out.
Thanks for the advice. Turns out it is just a tight fit over a splined shaft. Took a lot of pulling. I was only concerned because the Pro-Control Four has an LED built into the knob which, in reality, is just glued to the inside of the knob and a wire wraps one-turn around the shaft and exits through a hole in the faceplate to its connection on the circuit board.
The volume pot turns out to be a Noble unit encased in a three-section cast metal case with a circuit board attached to the outside. Once I got it out, I was able to remove two screws holding it together and get enough contact cleaner oil inside to then run out between the slightly separated case sections. Working the control sweep seems to have cleared it up and it is now back together working as it should.
I also pulled out another spare Pro-Control Four during the process, in case I decided to swap volume pots. The other Pro-Control Four (#3) had a non-working switched outlet noted since I purchased it off Ebay five-years ago. I had opened it up and determined that the relay that switches the outlet could be opened at the top allowing me to push the contacts closed to activate the outlet and then it would shut off when the unit was switched off. I figured it was a bad relay. A forum member, I believe here, years ago gave me the Mouser part number for that relay and I took yesterday as a good day to repair a second Pro-Control Four. No small repair as it required completely removing the entire circuit board to de-solder and replace the relay with a new one.
I carefully documented the wiring color and connections for power to the board with photos to help on reassembly. Got to use a Hakko FX-888 solder station I'd purchased years ago and never opened to get it done, then reassembled the board and two front plates and rear plate to test. Same issue. I noted the unit #3 had a "240" sticker on the transformer as well as "240" appended to the serial number, so I assumed this was built for Europe or military sale for 240v and maybe had been improperly converted to 120v prior to my purchase. Since I had two units out of the rack and recently disassembled, I took the case off the one with the repaired volume pot (#2) to check wiring. Not only were the transformer heavy wires a different color, they were attached to a completely different array of terminals on the circuit board.
I made an assumption that as long as I kept the wires with tracers from the transformer together and the non-tracer colors together, that simply matching their attachment to the board terminals with unit #2 might work . . . or cause a fire! Fingers crossed and making sure my wife knew where we kept the fire extinguisher, I powered it up with an outlet tester plugged into the switched outlet. It worked as designed, and tested it with an iPod and headphones. Now I have three working Pro-Control Fours in my house, and a justification for why I have duplicates of hi-fi equipment I love!
For posterity:
Unit #2:
Unit #3 before re-wiring:
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
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