Oscilloscope arrives!

I haven't touched the amp project since getting parts at the Hamvention early last summer. I hope to spend some time on it over the next few months though. Today I finally got my hands on an oscilloscope. Thank you Mike! It is a B&K Precision Model 1461. I am not sure how old it is but I would bet 15-20 years. It appears to be in nice shape. I don't know much about these so I will have to do some reading before I even turn it on. One sour note, B&K Precision doesn't provide support directly for their older equipment. They transferred the rights to the technical documents, to a subsidiary. This company wants $25, plus shipping, for the 35 page owner's manual! I may end up spending the money though.

Hamvention 2008 - Dayton, Ohio

The only other time I've been to the Hamvention (or Hamfest) was about 30 years ago. It is still big. Way too big to be taken in thoroughly in one day. Tickets at the door were a steep $25 but that is good for all three days, inside and out. It really is targeted at amateur radio folks, but all kinds of electronics are available in the flea market. Of course my interest was in parts for the Fender Champ 5E1 I am building, as well as tubes for the Hammond AO-35 that I just acquired. In that department I got the following: EL84(2), 12AX7(2), 5Y3(2), 12AT7(1), 6V6GT(1). Two are used, the rest are new. I paid an average of $7 per. New tubes like this would run me $12 and up not including shipping. I also got I handfull of high-voltage caps, four tube sockets, and some IEC 320 sockets (for AC power cables). I found a turret board with capacitors and large pilot lights attaced for $2, and a pile of selenium rectifiers for $5. The best, and least expected, deal of the day was the 3-phase VARIAC I found on the way out of the show which I paid $20 for. I hope to use this to slowly power up amps when testing. Since the flea market is so large, some folks use wagons or backpacks to tote stuff around. I met a guy who had the gest solution I've seen. He built a cart from angle iron, which holds milk crates and coolers, with two PVC tubes in the back for antennas. He actually mounted a spare wheel and tire underneath in wagon, just like a truck. You can see this in the photo at the bottom of this post. Remember to go to my actual blog and click on the photo thumbnails to open larger photos.

Organ Amp #1: Chassis AO-35 from a model M100

My co-worker Ron Ashcroft has graciously donated this reverb amplifier from his old Hammond M100. The unit is designed to take a signal from the driven reverb, sending it through an ECC83, a 12AX7 which splits the signal to drive two 6BQ5 (EL84). The bottom image is a schematic.

Console #3: Olympic Model 1770

This is a tube fired AM/FM turntable stereo console made in the early to mid '60s. The original purchaser/owner of this was asking $20. It likely has some parts I could use, so even though it didn't power up I actually paid $10 because there was an obvious sentimental attachment for the owner. It appears to be a cheaply built, in Great Britain I believe. The turntable is marked BSR. The circuit arrangement is rather curious. The lower image below shows the tube configuration. It appears that the preamp chassis is separate. Another oddity is the lack of power transformer.

Console #2: RCA VHT-46

This was another free listing in Craigslist. It is solid state console produced in that late '60s. I don't yet know what parts from this will be useful for my amp.

Tube testor works...I guess.

I bought this tube tester last year, probably before I retrieved the Magnovox console. This Century model FS-2 was made in the late '50s or early '60s. I hadn't tested it or tried to use until today. There were NO diagnostics or self-test described in the manual, so I had no real way of knowing if it works. I read the instructions and plugged it in. No sparks or explosions. I tested the REALISTIC brand 12AX7 which I pulled from the Magnovox, as well as a 5Y3 and three 6L6GT tubes which were in a batch of (over 100) tubes that came with the testor. The 5Y3 is a CROSLEY brand and it tested fine. But only one of the 6L6GT tubes tested OK and it is a SHELDON. Also visible in these photos are the two cold-war era Polish ammunition cans which will serve as a chassis for this project and possibly for my tremelo and reverb unit too. I have choke transformers also, so the only major component that I am still missing is an output transformer.

The power transformer works!

And I have a scorched test lead clip to prove it. Though a poor choice of conections roasted a test lead, there was no fire and the transformer wasn't damaged. This transformer produces 320VAC and 6.2VAC, but it since there is no HV center tap I will need to use a modified rectifier circuit.