Mc240 Rebuild - Question and Progress

Better copies of the sketches, no longer upsidedown:

higher res Cap Sketch
https://www.dropbox.com/s/bgju3kifxkh4hfl/board Cap sketch.JPG

You will notice that most caps attach at the top and bottom terminals of the same row. This changes for C19 and C20. C19 attaches at term 22,top to term 23,bottom. C20 attaches at term 23,top to term 24,bottom

Higher res Resistor Sketch
https://www.dropbox.com/s/cekavchv8s3a8wa/board resistor sketch.JPG

High Res Schematic
https://www.dropbox.com/s/54poz0stgkwhqsk/mc240 high res.jpg
 
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Your sketches should help me.He placed the jumper on the far left side of the board between 21-23 by your sketch I think.I am now wondering if he moved any of the wire leads coming from the power supply sections.I will use your sketch tonight to check the wire board connections.
 
Your sketches should help me.He placed the jumper on the far left side of the board between 21-23 by your sketch I think.I am now wondering if he moved any of the wire leads coming from the power supply sections.I will use your sketch tonight to check the wire board connections.

My sketch doesn't show the jumper that is between 17 and 18 middle term, I missed it. But there is no jumper between 21 and 23 on the resistor side of the board. There is a jumper on the cap side. White wire going from 21 top term to 23 middle term. It's difficult to make out the wire paths under the caps but once I pull the caps I'll be able to photograph them.
 
New toy. I've been using my buddy's Weller WES50 and really like it. Decided to buy one because I'm enjoying the heck out of this project. Went to find one and it has been replaced by WES51. Enough quality issues in the review that I started looking at other options. Hakko FX888D had great reviews and was under $100 so here I am. So far pretty nice station. Heats to 800 in about a minute.
 

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Side note, every resistor I've pulled so far has measured in spec. A few were close to the upper limit of their tolerance but all have tested good.
 
The black jumper wire that he put in on the left side of the resistor side of the board is what I question.I will look it over this evening with the schematic.
 
The black jumper wire that he put in on the left side of the resistor side of the board is what I question.I will look it over this evening with the schematic.

Yep. That wire was originally white and on the cap side, run under the caps. So the circuit is correct, the position of the jumper is just different than factory.
 
Yep. That wire was originally white and on the cap side, run under the caps. So the circuit is correct, the position of the jumper is just different than factory.

That is correct. Can't see it in the cap side photo you posted as it's cut off, but it may have been a cold solder of the original jumper when you replaced those caps. Looks like he did the easier more accessible method of wiring a new jumper in its place rather than pulling the caps to get to it.
 
I will check it tonight with the schematic.It looks like he ran the jumper between where two 56k's connect and a lead of the center 1 meg resistor in the cluster of 3resistors.I can't tell the values of the tan Dale resistors,but I think they are 1 meg.
 
The jumper that the tech placed is correct,although I believe that there must be a original jumper under the caps since I did not alter any of the wires when changing the coupling caps.The jumper that he placed is between R29(56K) and R60(100K) which connects those resistors to the -150v leg of the powersupply. I now question why the tech put two diodes in series for each of the three diode positions and if I should leave it as he has it or put it back to a single diode for each position.
Dave
 
The jumper that the tech placed is correct,although I believe that there must be a original jumper under the caps since I did not alter any of the wires when changing the coupling caps.The jumper that he placed is between R29(56K) and R60(100K) which connects those resistors to the -150v leg of the powersupply. I now question why the tech put two diodes in series for each of the three diode positions and if I should leave it as he has it or put it back to a single diode for each position.
Dave

I'm no expert but from what I've read there are essentially 2 properties of diodes that would matter in this case. The voltage drop across the diodes and the speed of the diode.

Voltage drop is what it is, a diode 'costs' a small amount of voltage to function. Older diodes 'cost' more. Newer diodes are more efficient by a good amount. It may be that he is trying to get the voltage drop across the pair to equal the voltage drop across the single original 1960's diode.

The Speeds of diodes has also increased significantly. The Speed refers to how much time it takes the diode to switch from blocking voltage to passing voltage. When it blocks voltage, there is a recovery time after the current switches back to the 'flow' direction before the diode will allow current to flow. Diodes today are much faster than diodes of the 1960s. He may have been trying to slow them down by chaining them as the second wouldn't see current until the first recovered, essentially stacking the recovery times.

Take all that with a grain of salt. That is all info I read from the net and applied to your question a few days after I learned it for the first time. I could easily be wrong.
 
Thanks for that analysis of the diode properties. I know that he used high speed diodes,although I had replaced them 4 years ago with diodes from Jim,which I believe were also high speed.I have read posts by Terry where he says that he doesn't like to use high speed diodes...I'm going to check voltages and if they are right I will leave the diodes alone.I'm still trying to contact the tech on A.A. so he can tell me which resistors should not be MF.I believe that carbon film would be the type to use.I will post his advice when I talk to him.
Dave
 
Thanks for that analysis of the diode properties. I know that he used high speed diodes,although I had replaced them 4 years ago with diodes from Jim,which I believe were also high speed.I have read posts by Terry where he says that he doesn't like to use high speed diodes...I'm going to check voltages and if they are right I will leave the diodes alone.I'm still trying to contact the tech on A.A. so he can tell me which resistors should not be MF.I believe that carbon film would be the type to use.I will post his advice when I talk to him.
Dave

I'm looking forward to his response as well. I'm holding off a bit hoping to have an answer before I start re-populating the board.
 
They met the OEM spex with the OEM parts, upgraded parts should give better upward overall spec margin.

Sent from my SM-N900V using Tapatalk
 
They met the OEM spex with the OEM parts, upgraded parts should give better upward overall spec margin.

Sent from my SM-N900V using Tapatalk

I agree with that. But then there is the whole "carbon 'sounds' better" camp along with the PIO Caps sound better camp. I really wish I had a couple of these to build with different components to test that.
 
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