Podcasting since 2005! Listen to Latest SolderSmoke
Monday, February 8, 2021
A Quantum Mechanics-based Receiver. The Rydberg Detector
Sunday, February 7, 2021
A Really Nice Video about a Regen Receiver
Saturday, February 6, 2021
Some Thoughts on Singly Balanced Mixers with Two Diodes and One Transformer
Wednesday, February 3, 2021
Shuji Nakamura -- The Inventor of Juliano Blue LEDs
He is the 2014 winner of the Nobel Prize for Physics. He is the person who figured out how to make blue light LEDs through the use of an Indium Gallium Nitride semiconductor. I was reading about him this morning in "Conquering the Electron" by Derek Cheung and Eric Brach. Thanks to Nakamura, the numerals on all my frequency displays glow in a pleasing Juliano blue. Three cheers for Nakamura!
More on him here:
https://www.trumpf.com/en_US/presse/online-magazine/nobel-price-winner-nakamura-wants-more-light/
Monday, February 1, 2021
The VFO that I am looking for: The Globe VFO deluxe
Sunday, January 31, 2021
Repairing My Maplin Audio Waveform Generator
Wednesday, January 27, 2021
Hyderabad Field Day
Hams in Hyderabad, India held a Field Day this week. That looks like a uBITX next to that HT. FB!
More info here:
Tuesday, January 26, 2021
SolderSmoke Podcast #228
Of course, no travel.
But vaccines are here so maybe soon we can leave our shacks.
In the meantime:
I’ve been playing chess against AI bots on chess.com.
Netflix recommendation: The Bureau. From France. A review from NPR:
A reading from "Conquering the Electron." Germanium vs. Silicon.
Bill’s Bench:
The KLH Model Twenty-one II.
Acoustical Suspension. First receiver
WITH A PILLOW! Bad speaker? Blown AF amp
finals. Hot heat sink. VBE Multiplier. Desitin.
Tony Fishpool’s recommended LM386 boards. 10 for 11 bucks. Nice. They
work. Pictured in the Amazon ad at the
upper right of the SolderSmoke blog page.
Putting a digital display on the Lafayette HA-600A
Test gear trouble. My
Radio Shack multimeter getting flaky. I
many need something better. Auto
ranging? My beloved Maplin AF generator died – will have to fix. I need that
thing. Probably a bad chip. Good thing they are socketed.
I almost forgot about SKN!
But I remembered and I made one contact with the HT-37 and Drake 2-B.
Pete’s Bench:
Presentation to RSGB on Homebrew.
TenTek Troubleshoot.
Swan 240? Looking
nice.
SDR adventures.
MAILBAG
Bill N8ET sent me some really nice Showa 9 MHz 8 pole
crystal filters.
Kevin AA7YQ Smoke jumper!
Building a hybrid SDR.HDR rig.
Launched blog. FB
Nick M0NTV working on similar HDR/SDR project. Great video.
Grayson KJ7UM Hollow State Design – Launched a new
blog. Very FB!
Thomas K4SWL of SWL Post blog. Kearsarge Mountain Transmission system. And recent events.
Peter VK2EMU Poetry.
CW poetry.
Pete WB9FLW looking at DSB rigs…
Drew N7DA Feels not
like a real ham because he hasn’t built a quad from bamboo. Which type of
landscape bamboo is best for antennas?
Ryan Flowers of MiscDotGeek.Com blog is also watching the
Tally Ho YouTube videos of Leo Sampson. Wants to put a WSPR beacon on the Tally
Ho.
Joe KF5OWY Working
with diode ring mixers, trying to see the mixer action on his ‘scope. 1 and -1!
Jim AB9CN sent a cool idea about how to do a 20/17 Moxon.
Roy GM4VKI – I thanked him for his article in SPRAT about
putting a 2n3904 on the output of an NE602 10P mod. Brilliant.
Roger Hayward Told him that I really liked his Dad’s recent
web site updates.
Farhan – Jokingly cursed me for showing him the Oscillodyne
regen of Hugo Gernsback and Jean Shepherd. “Now I will have to build this!”
Sunday, January 24, 2021
VBE Multiplier Makes KLH Receiver "Cool Running"
Yesterday I turned to the SolderSmoke wizards for advice on how to fix my KLH Model Twenty-one II FM receiver. I had finally gotten the thing working -- it wasn't the speaker, it was the AF amp, probably one of the final transistors was blown. I replaced the finals and the driver. For the finals I used a TIP29C and a TIP30C. For the driver a 2N3906. With this fix the receiver was sounding good, but the heat sink on the AF amplifiers was way too hot.
If you look at the comments in yesterday's post, you will see some great suggestions on how to fix this problem. The comments and Google led me to Alan W2AEW's YouTube channel and his video on a circuit called the VBE multiplier. Voltage Base-Emitter multiplier. I'd never used this circuit before. It allows you to adjust the bias on the bases of the two transistors in a push-pull amplifier.
This morning I built the circuit on a small piece of PC board. There were just two components: a 10k trimmer pot and a 2N3904 transistor.
With the little board installed, I adjusted the pot for a 1.2 volt difference between the bases of Q6 and Q7. I ended up with base voltage values almost identical to those called for in the KLH schematic.
The receiver sounds very nice now, and is no longer on the verge of bursting into flames. I even made up my own version of the pillow that KLH claimed was necessary for proper acoustic suspension.
Sometimes it is nice to be able to listen to something other than the chatter on the ham bands. And it is fun to do so with a receiver that you have worked on.
I even used some Desitin as a substitute for heat sink compound.
Thanks to Rogier for the receiver, to ZL2DEX, K0EET, W2AEW and David McNeill for the good advice. And to Dale K9NN who sent me a box of parts from which emerged the 10k pot I used in this project. Thanks guys. 73
Saturday, January 23, 2021
KLH Model Twenty-One II AF Amplifiers Too Hot. Why?
I've been working on this nice old FM receiver that Rogier PA1ZZ sent me. When I first tried it, it sounded terrible. I thought it might have been the speaker, but the speaker is fine. There was clearly something wrong in the AF amplifier. Schematic above. Click on it for a better view.
I ended up replacing the complementary pair of output transistors (Q6 and Q7) . The original had house brand designations -- I wasn't sure what to replace them with, so I just used a TIP29C and a TIP30C. With these transistors in there, the receiver sounds good. But the heat sink on the transistors is getting way too hot. I think the AF amplifier is now pulling about 1.4 amps, which is too much.
Another thing I did: I thought Q4 and Q5 might have been bad, so I replaced them with a 2n3904 and a 2n3906.Why do you guys think the heat sink is getting so hot? What should I do? The supply on this receiver is 25V DC.