Scott 299 schematic error?

thornev

Super Member
I just purchased a Scott 299, later version I believe. I've done tons of research, downloaded schematics, operations manuals, etc etc. I'm ready for a restoration. One of the first tasks is to replace the can caps. I read a 299 parts list and it claims that there exists a C5-C in the C5 can. I've scoured the schematic and I can find no such capacitor. I believe there are 2 versions of the original 299 (OT's along side of chassis and OT's along back) so maybe I have the wrong schematic. I don't know how to differentiate between the early and later 299 schematics.

Another discrepancy is that the parts list claims the C6-C cap is 10uF, but the schematic reads 100uF.

I should confess that both the schematic and parts list are SAMS, not the original documents from HH Scott. I've got the original Scott schematic, rev 6, in the Operations Manual. I cannot find an original Scott 299 parts list anywhere online.

Would anyone with a 299 let me know about the C5-C and C6-C please? Thanks, Thorne
 
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Shooting from the hip, I have both early versions of the 299 but packed away temporarily. Sams did make several mistakes from time to time. The original 299 schematic, first generation with the horizontally mounted output transformers is not something I have seen. I will check later if you don't get an answer. Remember, there are two versions of the 299 before they came out with the 299B The second version of the 299 looks a lot like a 299B.
 
Thanks, kvflyer. I do know that the OT's were first mounted along the side of the chassis and then later along the back like the 299-B. I have the later version (I shouldn't have said I purchased the early version. I've corrected that post). I just printed a Scott 299 schematic. It is dated 26 Sept 1958. As I said, I don't know how to determine if it's the early or late version schematic.

Scott marks on the schematic the can caps in a non-standard fashion. There is no '+' and '-' marking for lytics. There is the shape indicator (semi-circle, square and triangle). And the tube numbering is weird too. All channel A tubes are "Vn" (1-99) whereas channel B tubes are marked "V1nn" (100-199). Anything not in A nor B, like the rectifier, is labeled "V2nn" (V200-299). It looks like the same applies to capacitors and resistors - Anything in channel A is 1-99. Channel B is 100-199. Anything outside A or B is 201-299.
 
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There are more than a few ‘discrepancies’ in the old Scott schematics. When replacing caps, I don’t rely on the documentation but replace what is actually on the chassis (ie: make my own parts list).

There are quite a few Scott schematics in the AK database. Did you look there?
 
njcanuck - Yes, I checked the AK db. That's a great idea to correct the schematic with the actual part numbers in the chassis.

Dadbar - I have the VTV12 (page 19) as well as the VTV20 (page 29).
 
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If you look at a lot of schematics from the same era you will see that in a tube circuit of similar design the capacitor values will be in the same general range. For example, the first cap of a 5ar4 tube will be around 50uf x 500v. The second cap will be about the same value. The cap on the cathode resistor bypass is 50 to 100uf. The caps on the preamp tube power supply is around 20 to 30 uf. It gets tricky with the small value, uuf or pf, caps which are more precisely tailored to fit the circuit. So, if you run across a value that seems to be wrong for the application, you should be suspicious and do some checking.
 
When you look at these schematics for the 299, please don't make the mistake that I made. There is a capacitor in the HH Scott Schematic, C8 and C108 and in the Sams, C18 and C46 listed as .22. That is not µFD. That is a ceramic capacitor, probably .22 pFD and it is doubtful that it is bad. I changed them in my amplifier and what a squeal! Thankfully, I was able to put the originals back into the amplifier.
 
Thanks for the warning, kv. I've marked my schem. I wish I could find a non-SAMS parts list.

What is the "D" in "pFD"? I've never seen capacitors displayed as anything but pF, nF and uF, or multiples of the units such as uuF, etc. Thorne

PS - I just checked all the schematics for the 299 series. They are all marked as .22 until you get to 299-C in which C8 amd C108 are marked .0047. But it looks like those caps are used differently in the 299-C. It looks like the C8 and C108 equivalents in the 299-C are C9 and C109 and they are marked .68.
 
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Pico Farad, the "D" in farad. I guess that was not the correct way to type it. Thanks for noticing it. Just don't change those little buggers!
 
I am from the old school (70 years old) and still have to get the chart out for the new resistor band colors, five bands or six bands etc. And the conversion from pf, to mmf to nf etc. is taxing. Also, capacitors now have numbers like 104 instead of .1µFD etc.
 
Keep in touch. I have much HH Scott equipment and it is my favorite. I do have Fisher as well.
 
Me too, kv. I've restored a Fisher 500-C and a Fisher KX-200. This is my 1st Scott. I also have a Marantz 2265B that I paid to have restored. Thorne
 
I just realized why the SAMS and Scott schematics for the original 299 are so different. The SAMS schem is for the early 299 version (with the OTs along the chassis side). The Scott's schem is for the later 299 version (with the OTs along the back).
 
I'm really confused. The 299 Operations Manual in Appendix C, number 3-E, says to check the bias, measure "filter resistors R209 and R210, two 330 ohm 10 watt wire wound resistors connected in parallel." I've got the 299 schematic, not the SAMS version, and there is an R209 that is 160 ohms but no R210. The schematic skips R210 and goes right to R211. It also skips R206. I checked the SAMS schematic, just in case, and it doesn't have those numbers at all.

PS - I found R119 and R120 on the SAMS schem and they are both the 330 ohm resistors in parallel the Operations Manual references. WTF??? The Operations Manual contains a schematic that doesn't contain these 2 resistors that it references on other pages !???
 
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My 299, first generation has two resistors in parallel. 330Ω resistors which would work out to 165Ω. Scott made many changes over their production runs. For instance, if you look at the Scott produced (not Sams) 299 schematic, you may (or may not) find the revisions. The copy that I have has 6 revisions with the date. A lot of what we have to do is try to reason what or why something was done. If a part looks original to the amplifier, and it doesn't match the schematic, two things come to mind. It was a later production change or an earlier model that was produced before the schematic that we have.

The 299C had at least 7 various versions during production. No doubt the HH Scott service centers had all of the revisions. But that was 50 years ago. I just feel very fortunate for what information survived the trip to the bin.
 
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Thanks, kv. You're right. I'll have to wait until the unit arrives to see what I've got and alter the schematic accordingly. I just hope there's a schematic for what I get because if there isn't, I don't have the knowledge to do anything but replace with the values of what is in the unit. Well, and rely on you and others on this forum to help me. I should have known this wasn't going to be easy when I saw there is no forum anywhere dedicated to Scott equipment. Oh well. I'll keep my fingers crossed that this unit doesn't need too much fixing and offer you and others whatever beverage you prefer. Thorne (smile)

PS - Thanks for the picture.
 
Finally got my 299. So many questions.

I want to add cathode resistors to all 7189 tubes which would be at pin 3 and the other side to ground (so I can measure the voltage and then set the appropriate bias). All the pin 3's are tied together. Do I leave them tied together or do I remove the wires? I've done this before with a Fisher 500-C, but I don't remember that the cathode pins were tied together.

There's this huge orange-ish what looks like a ceramic capacitor connected to the back of the fuse and to the extra outlet (see attached picture #2). It has markings "125VAC, MR, .01 +- 100%, M inside a C and the number 64". I thought it might be a thermistor. Anyone know what it is? It's not on the schematic so someone added it. I thought maybe it's a reservoir capacitor (rippler smoother), but it's in the wrong location for that.

kvflyer... I just finished reading your thread on your 299 version 2 rebuild. Great stuff ! How do I know if I have a Selenium rectifer or not? I attached a picture #1. The schematic indicates that it's a bridge rectifier with the 4 diodes, but I found pictures of Selenium rectifiers that look just like what's in my 299.
 

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