Posts: 16,476
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Terry just couldn't stand the thought of me leaving without anything to repair so he made me take his Tektronix 465 scope to look at.
Once powered, it looked like the H-sweep amp malfunctions: I can see the flickering but cannot find the beam.
Sure'nuff, once I started to look at the H-output amp, I found a bad 2N2222A transistor. The Emitter junction is open. Q1274 namely, if someone wants to bother looking.
Another thing, the 110V power to the output seems to be 150V. Wonder why.
Anywhoo, Terry, if you have 2N2222A little buggers, get me some by mail.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 7,295
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Oh you mean the 2n2222a the most popular transistor on the planet??? For a guy who mostly services vt stuff I'm pretty sure I have some.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 05-15-2017, 11:46 PM by Radioroslyn.)
Posts: 16,476
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
I will see if we have anything close in junk at work. I do not have any at home - no need for them......
PS. Was able to solder gold-plated lead clippings I save (come handy!) to an SMT SOT-23 MMBT2222A transistor which is pretty much the same device. Will try tonight.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 16,476
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
OK. Came after 9pm home from grappling class, decided I had just enough energy left to attempt the repair.
The culprit. 2N2222A transistor.
The sub. MMBT2222A, SOT23 with leads soldered, inserted in the socket.
The channel lines, chopped.
The channels showing the test meander signal from the scope front panel itself.
Ideally, Terry, if you have a 2N2222A, you could put it in, though I think this one is just fine. SOT23 dissipates half of what TO-18 can, but then I do not think there is much dissipation here.
About 1.5hr for the whole thing. Not bad. I never fixed a scope before.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 7,295
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 16,476
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Yeah I saw that picture on some tech forum where a guy was trying to fix his 465 
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 3,148
Threads: 56
Joined: Apr 2011
City: Lexington, KY
Great job Mike!
Terry Layman just bought a batch of test equipment and I checked his three Tek scopes for him. The 465 powers on with no trace, the 485 seems dead, but the 475 seems to work OK. So if you want to hone your scope fixing skills I'll let him know 
John KK4ZLF
Lexington, KY
"illegitimis non carborundum"
Posts: 16,476
Threads: 573
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
I thought I never get to fix this one until late summer, as I am deep into 38-690 now.....but it is in waiting for the rebuilt electrolytics which I have yet to cut open and I had a little intermission, so I got to the scope.
It's fun to fix solid state, plus this is something I really know quite a bit better than vacuum technology.
But as everywhere, one's got to be methodical in diagnosing, poke, smell and listen
I have to give proper dues to my mom when it comes to good diagnosis: she was a medical doctor in her pre-American life, and was considered the best everywhere she worked, and for a good reason. She once kind of opened my eye to how to diagnose: pay attention to everything, undress the patient fully and do not be afraid to ask questions, even if people around think the questions are silly. Helps a lot.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Users browsing this thread: 1 Guest(s)
|
|
Recent Posts
|
|
Zenith H725
|
| I just remembered, I have some hi temp silicone rubber material which could do the trick. Or a piece of FR4 laminate. Th...EdHolland — 08:39 PM |
|
Zenith H725
|
| The PSU filter cap arrived today (thank you USPS!) so I will work on that later.
Meanwhile, I have the dial, speaker...EdHolland — 06:42 PM |
|
Philco 610B oscillator wiring
|
| Thanks Terry. After checking my notes I think I recorded about -10v at the 6A7 G4/control grid. The screen grid (G3 &...Tubester — 05:59 PM |
|
The list of my radio & TV collection!
|
| Magical chords of forgotten melodies, old nostalgic music on an old radio... Saturday night blues on the Mid-Waves on an...RadioSvit — 12:20 PM |
|
Philco 42-345 Restoration/Repair
|
| Thank you MrFixr55 the issue with this radio is that the internal coil antenna is missing and there was a wire in its pl...osanders0311 — 11:34 AM |
|
Philco 610B oscillator wiring
|
| Regarding the oscillator circuit which is comprised of the 6A7's cathode, control grid, and screen grid. These elements ...Radioroslyn — 10:33 AM |
|
Philco 42-345 Restoration/Repair
|
| Hi OSanders,
First off, welcome to the Philco Phorum where Phine Phamily-Phriendly Pholks Phull of Philco Phacts and P...MrFixr55 — 08:41 AM |
|
Philco 42-345 Restoration/Repair
|
| Today I've been reading through the site trying to learn more about this radio. I also soldered the lose power cord cabl...osanders0311 — 08:24 PM |
|
Philco 610B oscillator wiring
|
| Thanks David! I do have that same later prodution model 610 schematic. I've also studied the Philco service bulletins fo...Tubester — 08:12 PM |
|
Philco 610B oscillator wiring
|
| Some info from Beitmans says late production. David David — 06:06 PM |
|
Who's Online
|
There are currently 1865 online users. [Complete List]
» 2 Member(s) | 1863 Guest(s)
|
|
|
|
 
|
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
