Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Vol control ?
#1

I have an American Bosch 04 http://www.nostalgiaair.org/pagesbymodel...022251.pdf 
the second print is the one. 
The vol control is open and there is nothing on it besides I'm pretty sure it is not original. I have tried pots from 5k to 500k and all I get is a whisper out of it with it at max. I have about 25' of wire strung in my garage for an antenna. What am I missing? #7 is 48k and #5 is .1uf . Thanks

Eric
#2

Eric Have you changed the caps in it and tested all the tubes? If not that, I would check the antenna coil. I would also ck R7, C3 and C5 not saying its the problem but where I would start. Also did you do voltage checks on the tubes?
If I'm not close on my advise someone will see this and get you in right direction. Good luck.
#3

Hi Eric,
The volume control is going to be a fairly low value as it is in the ant circuit. Probably 10K to 20k should be about right. As Mike said it important to replace the caps and then you can measure voltages to figure out what going on. Without replacing the cap you run the risk of burning up the power transformer which you don't want re replace. It special cause it has a 2.5v filament winding very hard to find.
If you have done the replacements measure the voltage on the plate of the 47. That would be on pin 2.

Terry
#4

(07-26-2015, 06:21 PM)Radioroslyn Wrote:  Hi Eric,
The volume control is going to be a fairly low value as it is in the ant circuit. Probably 10K to 20k should be about right. As Mike said it important to replace the caps and then you can measure voltages to figure out what going on. Without replacing the cap you run the risk of burning up the power transformer which you don't want re replace. It special cause it has a 2.5v filament winding very hard to find.
If you have done the replacements measure the voltage on the plate of the 47. That would be on pin 2.

Terry

Thanks guys, 
Probably should have posted all I have done so here is what I have
All tubes tested and are good.
Re capped all.
I have replaced the resistors ( not that many and the dog bones were mostly way over)
2.5V filament ?  The 25z5 and the 43 have 25 volt filaments. the ballast tube the 185R8 checks out also.
The voltages are as follows
            screen     plate    cath     Fil
25Z5       ----       118     -----     61
43         120        122     35       37 
6c6         52         40        5         6.3
6d6        122        120     .6        12
Some are off not sure why. I have checked the RF coils and there good tomorrow I 'll do the ant.  
 
#5

Sorry I was looking at the 1st schematic, it has 2.5v tubes.
As you may know this is a TRF set consisting of a RF amp a detector, and audio out. The plus is it's pretty simple the down side is poor sensitivity.
The cathode voltage on the 43 seems a bit high but it does use a 600 ohm resistor in the cathode. Most I've seen are a bit lower around 300 ohms.
Double check your ant coil and then use a good ant read long and high up.

Terry
#6

(07-26-2015, 08:51 PM)Radioroslyn Wrote:  Sorry I was looking at the 1st schematic, it has 2.5v tubes.
As you may know this is a TRF set consisting of a RF amp a detector, and audio out. The plus is it's pretty simple the down side is poor sensitivity.
The cathode voltage on the 43 seems a bit high but it does use a 600 ohm resistor in the cathode. Most I've seen are a bit lower around 300 ohms.
Double check your ant coil and then use a good ant read long and high up.

Terry

Found my mistake it was on the 43 tube part 13,14,15 had these wired wrong. To be fair I started this radio when I first started the hobby ran into the dead end and put it on the shelf thinking I need to get more experience. The 5k pot works fine but I need to get one with a longer shaft, not a big deal!. thanks again for helping!

Eric 
#7

Glad to be of help. Depending on how long a shaft you need I've used a piece of 1/4" hose has a coupler to another shaft. If it slips use a tieraps to secure it.

Terry




Users browsing this thread: 2 Guest(s)
[-]
Recent Posts
New Philco Repair Bench
I am sure this is the archive, and not the Chuck's site.morzh — 09:50 PM
Made mistake & did not label connection
It's not like we are good friends with that wire and can tell it from other ptetty identical looking wires. Why'n't you...morzh — 09:49 PM
Made mistake & did not label connection
I'm not sure why that wire wasn't covered in the video. I'm pretty sure the 6A8 won't work until that pin is grounded. Y...RodB — 09:47 PM
Made mistake & did not label connection
You'll have to forgive me, I am not sure what you mean.  Can you explain what you are really saying.  If anyone does not...georgetownjohn — 08:05 PM
Made mistake & did not label connection
Those are details better left to the ones who know. Maybe you disconnected the wrong end of the wire.RodB — 06:22 PM
Made mistake & did not label connection
Maybe this is starting to make some sense in my hard head.  Is this why the wire in question was not in the great Ron Ra...georgetownjohn — 04:34 PM
Made mistake & did not label connection
I was correct with the 6A8 pin connection's, 7 and 8 are connected to ground as well as the tube shield (the broken line...RodB — 02:41 PM
Made mistake & did not label connection
What does the dotted line representing that surrounds the tube in the schematic?georgetownjohn — 02:17 PM
Made mistake & did not label connection
Hello John, I have been there either label got lost or was not labeled ! Sincerely Richardradiorich — 02:15 PM
Made mistake & did not label connection
Sorry, it is a Philco 37-640.  Does that help?--Johngeorgetownjohn — 02:14 PM

[-]
Who's Online
There are currently no members online.

>