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As I was cooking my steak and potatoes (delicious btw, but that's a different thread) I thought about the NFB. The resistor value is calculated for a specific output ohms. So you have to use a different resistor if you're using 4 ohm for the secondary instead of 8 ohm. I looked up the...

This is the NFB circuit. The 22k is the NFB resistor, I forget what the 1.5k is called. This from Rob Robinette's site about positive feedback, which I have never personally witnessed but have seen online more than a few times "Since this amp uses negative feedback (NFB) there is a 50-50...

Am I not seeing this resistor 'cus it's hidden, or is the 22k resistor for the preamp power missing?

Hey, that's a great looking build. Those 5W cathode resisters get HOT and will fry capacitors that touch them. It would be prudent to have at least a Popsicle stick thickness in between it and the capacitor! I usually leave as much room as I can, but there's not a lot of room to play with on...

That is usually due to positive feedback instead of negative feedback. If I remember correctly you need to switch the wires from the tube to the output transformer. Oops, single ended. Try using the brown wire instead of the blue one.

I have a Lightning on the build list. It's been there a long time, and it's going to have to wait even longer, lol...

I like flipping around projects just because it feels like I'm working if I work on one too long. Plus being a (retired and loving it) programmer I'm used to 'hot issues' popping up and having to shelf stuff till the fire is put out. Just got my Metropoulos repro 2203 chassis on Monday...

Actually, thinking back it may have been purchased around February 2022. But yeah it was a good deal even then. The guy had five, and had sold 2. I read the feedback of the two people that bought it and they were very happy. I posted the link somewhere on this forum, and soon the other two...

btw, ended up getting an Owon SDS7102V for about $250.... like everything else the price has skyrocketed...

I saw one on Amazon a year ago when I was looking to upgrade to new tech from an *old* tetronix..

Hey I searched for OEI and found this. Apparently Heyboer made them and they can do a custom order...? I know that APD also has some custom spec'd heyboer iron

Well, meaning their PT's may not last long... The post was a guy reporting the same symptoms, a member that repairs amps had two different mono's come in around the same time with shorted PT's...

Oh oh. Trouble in paradise. A member of TGP is reporting receiving two Monoprices at the same time with shorted PT's!!!

OEI? I have Mercury Magnetics on the 1987 I built back in 2011 - schwing!!!! These are some of the mustard caps I was talking about, they were made for PCB boards, and have the short leads. Since I make my own circuit boards I just drew up a layout especially for them!

Hey, speaking about the chassis and faceplates I ordered a week ago, THEY'RE HERE!!!! Woo Hoo, now that's what I call one BIG ASS chassis!!!! Gotta admit, 6 x 50/50uf can caps, for a total of 12 capacitors for the power smoothing will be the most I've ever stuck on a chassis. I have all...

Metroamp kits were exact repro's of the original vintages marshalls all the way. Valvestorm is handing that side of the business now 'cus George is tooooooooo busy raking in buck$ on his amps! Check out the BOM on the PDF link. It's the complete instructions for a 100w. I ordered a 2203...

Just butting in, on old Marshalls you see only carbon film in the signals, and they are one watt. They do use metal film, the red iskra's, in some non signal positions. I've made over 20 5e3's and use only 1w CF in the 1/4w positions. Dumble's are also all carbon film.... I have a mojo kit...

And they’re prone to cracking in half and complete failure!

I know that when I'm putting together the parts, I use the best ones I can find. Many times kits have components I just won't use, like 1/4w carbon comp resistors instead of 1w carbon film. Rob Robinette, a navy trained tube EE, said the closer a resistor's rating is to the current the more...

Just to chime in, a common problem in amps that displays this same symptom is when the input/output jacks become corroded or just covered with muck. You might try cleaning them.