I had to finish the testing of the prototype 833A output transformer in a hurry. I spent two hours trying to blow the 833A prototype amp up by playing guitar through it at extreme volume levels, complete with feedback and hard clipping. No dice, the amp just kept putting up with my S***, although I did blow the bench circuit breaker twice. I started a new 833A page to present these results. There are pictures and some data from an 833A amp that was temporarily assembled to test a prototype output transformer. The amp took up all of one work bench, and part of another. I put it together in a big hurry (3 hours) and it shows. I got over 200 Watts RMS from this thing, and it took some ridiculous abuse without complaint. All good things must come to an end, and this is no exception. I have already disassembled the amp.
The revised SE amp instructions are finished and an amp is being built currently. I will be out of town for most of August. The SEamp boards will be offered for sale when I return. This will be in early September. I will be working a zillion hours a week before I leave so this might be the last update for a while.
I was asked, " Why did you need to rewrite the manual. Was it too hard to follow?" No the manual was (and still is) easy to follow. The original test and adjustment procedure required making voltage measurements on a live board, and simultaneously adjusting the bias. This is no problem for an experienced builder, the original target user. It became apparent that many inexperienced people wanted this amp. I worked with two of the early consumers to devise a test and adjustment procedure that first timers are comfortable with. This is the multiple meter method outlined on the safe meter use page. This procedure separates the user from the electricity, making the procedure safe for newbies and experienced users alike. Now that digital meters are as cheap as screwdrivers, there is no reason not to have a few.
I have not had computer access for the last two weeks. Bellsouth (our ISP) was down most of this weekend. Even though I live in a major metropolitan area, all I can get is SLOW dial up, and that doesn't always work. I just got to my email. I have tried to answer everyone as best as I could. The answers to the common questions about the board status is below.
I sold a few boards to some inexperienced people at work to get their feedback on the assembly manual. I gathered their inputs, and made revisions. The revised manual is almost finished. The safety and safe meter use pages were done at their request, yet these pages get few hits. I will have some one build an amplifier using the new instructions before putting the boards back up for sale.
Unfortunately, my father became ill before I was done and I spent each weekend at his house (80 miles away), or at the hospital. He passed away last weekend, hurricane Dennis visited this weekend, and the funeral is now scheduled for next weekend. My mother needs care, and the legal arrangements need to be taken care of. Since the weekends are when I usually work on this, not much has happened. I can't say exactly when I will get it all done.
I plan to upload most of the basic assembly and checkout instructions to the web site, so that a potential builder can see what is involved before purchasing a board. I can't say yet when the assembly video will be done since I am new to digital video editing. I will post the progress on the web site.
I got a question about the picture of the amplifier shown above. Won't the transformers interact since they are so close together? Yes they did! Since that picture was taken I have rotated the power transformer 90 degrees to correct a hum that could be seen on the FFT analyzer when the amp was first switched on. Oddly enough the hum disappeared as the rectifier tube warmed up. Sooner or later I will take new pictures. The hum was only barely audible with my ear to the left speaker, but might have been a problem with more efficient speakers.
I have plenty of new information to add to the site, just no time to do it. I have an 833A SE amplifier running on my bench. It puts out over 200 Watts RMS at 4% distortion. It uses the same SE amp PC board. I will put the details up when I get caught up with all of the ugly stuff.