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, 05:21 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, 07:51 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: 1 Guest(s)
[-]
Recent Posts
Philco 38-2 Low Volume
Both sch, the one you showed in the beginning and the one I see on Nostalgia, show 40K for the 2nd audio plate.morzh — 02:25 PM
Model 96 cabinet veneer
I can't figure out what the first step is, let alone the final step. I have tried copying pictures from my hard drive a...TGLager — 01:40 PM
Philco 38-2 Low Volume
I managed to get some more time on this. Hi Mr. FixIT, The radio has been recapped. Many of the resistors were rep...dconant — 01:39 PM
Philco 38-2 Low Volume
Thanks guys for the help. I started looking at these points but I have to quit for the day. I will be looking into this ...dconant — 12:23 PM
RCA WV-98c
Check out this crazy zero pot operation. Touching it drives it crazy. Its rubber tipped. Also the 6al5 has no negative v...daveone23 — 12:08 PM
Philco 38-2 Low Volume
If you check all of that and still have a problem (my first inkling would be one of the 6F6s) then look at the 6J5 phase...RodB — 10:44 AM
RCA WV-98c
Those will probably depend on teh switch combination. Could you list some that you see, their values and what they sh...morzh — 10:26 AM
Model 96 cabinet veneer
You are probably skipping the final step. Once you select the photos you want and they get downloaded, the system assign...RodB — 09:36 AM
RCA WV-98c
At this point, there is no input, just internal voltages Which are incorrect and not sure what they should be.daveone23 — 09:15 AM
Philco 38-2 Low Volume
Hi DConat, Generally, the lower the plate voltage the less negative the grid voltage has to be. Since the plates an...MrFixr55 — 09:27 PM

[-]
Who's Online
There are currently 1155 online users. [Complete List]
» 2 Member(s) | 1153 Guest(s)
AvatarAvatar

>