I am used to working with Sam's Photofacts and I am having a hard time figuring out component's values and location without it. Does anyone know if there exists a at least a parts list somewhere to go along with this schematic?

http://hhscott.com/pdf/340B_EARLY.pdf

Exactly what are you looking for? The schematic is pretty easy to follow. That schematic is the "Official" one made by the engineers at Scott. Usually, the parts value is written next to the part. Also, if you get a Sams Photofact, the numbering of the parts is a Sams thing and will not match the Scott numbering scheme.

Exactly what are you looking for? The schematic is pretty easy to follow. That schematic is the "Official" one made by the engineers at Scott. Usually, the parts value is written next to the part. Also, if you get a Sams Photofact, the numbering of the parts is a Sams thing and will not match the Scott numbering scheme.

There are diodes on the schematic that don't have any information about them. Additionally, I am having a hard time figuring out which resistors are which on the chassis as compared with the schematic, especially since there has been some drifting with them. Also, the Sams I have worked with, have been an exact match. Perhaps I was lucky with that. Even so, it is a lot easier for me to work on this stuff with a Sams on hand.

No parts list or Sam's available for the 340B. Get that color code action going for the resistors and each capacitor should have it's value clearly marked on it.

Replace the Selenium rectifier with a 4 Amp 400Piv

I replace the main PS diode with 8 Amp 600V Fairchild Stealth Diodes myself.

I personally never trust a schematic or Sams to be absolutely correct especially with Scott gear. Scott made umpteen changes through a model run and seems like they almost never released undated schematics.

The 299C - LK72 series amplifier is a classic example no less then 7 versions of that amp exists and maybe 2 or 3 schematics.

No parts list or Sam's available for the 340B. Get that color code action going for the resistors and each capacitor should have it's value clearly marked on it.

Replace the Selenium rectifier with a 4 Amp 400Piv

I replace the main PS diode with 8 Amp 600V Fairchild Stealth Diodes myself.

I personally never trust a schematic or Sams to be absolutely correct especially with Scott gear. Scott made umpteen changes through a model run and seems like they almost never released undated schematics.

The 299C - LK72 series amplifier is a classic example no less then 7 versions of that amp exists and maybe 2 or 3 schematics.

Craig is right on target here. I have an original HH Scott LK-72 schematic that lists the 7199 AF Amp/Phase Inverter. It is not the one on the HH Scott site, it is in the first generation LK-72 (often referred to as the LK-72A). The one on the Scott site has three revisions and uses the 6GH8.

Yes, they did make many changes within each model with no change of the model number. For example, I have a 222D that is clearly labeled 222D on its last generation extruded faceplate. But, by the control layout, it is a 222C. Later 222D models had the controls in a straight line. Mine has the controls separated just like a 222C.

As far as trying to locate the resistors from the schematic to the amp, I usually work from the tube pin-outs. Marking the tubes underneath will help too. Just be aware that just because the schematic may show a resistor coming right off a pin, it could be mounted somewhere else, that is "tied" to the pin. The schematic is showing things "electrically" and actual physical placement can be very different. This is where the patience comes in.:yes:

As far as trying to locate the resistors from the schematic to the amp, I usually work from the tube pin-outs. Marking the tubes underneath will help too. Just be aware that just because the schematic may show a resistor coming right off a pin, it could be mounted somewhere else, that is "tied" to the pin. The schematic is showing things "electrically" and actual physical placement can be very different. This is where the patience comes in.:yes:

Jay, your tip is much appreciated. :thmbsp:

I am in and out for the next few days. If you want to drop me a line with a question, I will be happy to get one of my 340B Scotts out and check something out for you. You can post here, PM or email; your choice. Gotta help those with Scott equipment!

I am in and out for the next few days. If you want to drop me a line with a question, I will be happy to get one of my 340B Scotts out and check something out for you. You can post here, PM or email; your choice. Gotta help those with Scott equipment!

I appreciate it. I am waiting for parts to arrive. My biggest challenge will be replacing the lytics as it is very tight under there and it will take some detective work to figure out which lug is what capacitance. I also need to figure out what kind of diodes I should order, as there are several sections of them and some of them have no markings on them or are there markings on the schematics.

Diodes are one of those "snake oil" areas.:D You can spend 20 bucks apiece or a 10 cents apeice. I use good old Fairchild UF4007s in commercial type amps like that. You can get them by the 50 or 100 roll most anywhere, then you'll always have plenty of diodes.:thmbsp:

http://www.mouser.com/Search/ProductDetail.aspx?qs=NwIfwa72FlplAHiXupLMBA%3d%3d

I appreciate it. I am waiting for parts to arrive. My biggest challenge will be replacing the lytics as it is very tight under there and it will take some detective work to figure out which lug is what capacitance. I also need to figure out what kind of diodes I should order, as there are several sections of them and some of them have no markings on them or are there markings on the schematics.

At the risk of sounding too simplistic, you can replace the power diodes with four 1N4007 diodes. I believe that Radio Shack still sells them. Usually pennies each. They are rated 1 Amp and 1000 PIV. More than enough. No problem with using bigger ones though. If I remember correctly, Scott used four individual rectifier diodes. They most likely are still good but for what new ones cost... And you are already there, must makes sense to replace them.

For the filters, the cans have markings next to the terminal, triangle, square, "D" and nothing. That corresponds to a marking on the outside of the cap. Should tell you which one is which. Of course you will have to do detective work to find out which one is which. I don't know if the new replacement "FP" capacitors come in the correct values for the 340B. On the downside, they are between $35-45 each; a little steep. Just take your time.

I know that the 340B has a lot jammed under the chassis. Not nearly as much room as a Scott LK72 etc.

I have three 340B, three 345 and one 380. Most are in queue waiting their turn at the soldering iron. Funny, I was all ready to do this when I retired. Now, 5 years later, where does the time go?

Pictures as you go? We will happily help. BTW, I live in Baltimore, MD...

Thanks guys, I didn't know that about the caps symbols and will have to take a quick look.

It is actually the diodes in what I think is the MPX section I am struggeling with. Could someone explain how diodes are valued? Also, if you look at the 340B early schematic, you can see there are diodes everywhere. Thanks for your offer to help. I should post some photos of the diodes. On the schematic, I see diode values of IN560/80m, IN294 and then some that have no mark at all.

I'm not a diode expert, but I think it's pretty much, current carrying ability, speed, and forward voltage. That's why the Fairchilds and RS ones are pretty much a "do all" for amps of this generation. They are actually a marked improvement over the fledgling diodes of that day.

I'm not a diode expert, but I think it's pretty much, current carrying ability, speed, and forward voltage. That's why the Fairchilds and RS ones are pretty much a "do all" for amps of this generation. They are actually a marked improvement over the fledgling diodes of that day.

Would it make a difference where it is? Obviously there are the rectifying diodes, but there are a few other in a different part (I think MPX section) and they are a different type than the rectifying ones. Also, could I connect the negative pole of a replacement electrolytic to the twist lock connection on a can? I assume it is a chassis ground.

I think I see what you're talking about (one of them ties to R215 no)? The RS or Fairchilds will do fine there.:yes: I often use the electrolytic lugs for grounding the caps that replace it. I figure that way I'm sticking with the original designers idea as far as ground currents. Don't let the insultated or positive can ones trip you up.:thmbsp:

I think I see what you're talking about (one of them ties to R215 no)? The RS or Fairchilds will do fine there.:yes: I often use the electrolytic lugs for grounding the caps that replace it. I figure that way I'm sticking with the original designers idea as far as ground currents. Don't let the insultated or positive can ones trip you up.:thmbsp:

Some are around
R526, C524, C525

Some are around
R557, R558, etc

Some are around
R215 as you say

and I think there are a few other. What do you mean by "Don't let the insultated or positive can ones trip you up"?

Some can caps are mounted on insulator wafers and do not ground to the chassis. Just be aware of these, but once again, if you use one of the old caps ground lugs you should be fine. I think you'd be fine with the RS or the Fairchild diodes for all those spots.:thmbsp:

Some can caps are mounted on insulator wafers and do not ground to the chassis. Just be aware of these, but once again, if you use one of the old caps ground lugs you should be fine. I think you'd be fine with the RS or the Fairchild diodes for all those spots.:thmbsp:

How do I tell?

How do I tell?

Just by looking at the mounting. Instead of the can being luged down right to the chassis, it will be on a brown phenolic wafer that is it itself mounted to the chassis. Many times you will see this on the bias supply can cap, or filter caps for the low signal tube supplies, or DC heater circuit cans.

Just by looking at the mounting. Instead of the can being luged down right to the chassis, it will be on a brown phenolic wafer that is it itself mounted to the chassis. Many times you will see this on the bias supply can cap, or filter caps for the low signal tube supplies, or DC heater circuit cans.

DC heater circuit and bias supply capacitors are can positive with reference to the chassis. For the most part, the filter capacitors are can negative with respect to the chassis. However, usually the electrolytic multi-section capacitors are mounted with the brown phenolic wafer. There may be a black wire going from one of the outer ring lugs on the filter capacitor to a ground lug somewhere on the chassis.

One thing to watch out for is the ground lugs that are riveted to the chassis. Since the chassis is aluminum and the lug is usually tin-plated brass or steel, there is a dissimilar metal condition. With humidity and age (this receiver is 44 years old) oxidation will often occur. There may not be a good solid connection to the chassis. I have drilled out those offending rivets and replaced them with a screw, star washer and nut. Problem fixed.

Now as for the diodes in the MPX section, I would not fool with them. At least get the receiver up and running, especially the power supply and the output section and go from there. I have never had to replace those diodes. They are often very small clear glass with a band on one side.

Just a thought...

Yeh, I wouldn't be changing the little glass ones.:no: They could be zeners or something.:sigh:

Yeh, I wouldn't be changing the little glass ones.:no: They could be zeners or something.:sigh:

They are not zener but I would not change them unless I was absolutely, positively sure they were bad. They could make the FM sound like a calliope when receiving/demodulating FM Stereo.

I'll post some photos later. It is much easier that way.

Understand....