Odd Globe Scout 680A

[n8fvj]

I just received a Globe Scout 680A and instead of having the 6SJ7 and 6C5 speech amp, it has a single 12AX7. It is factory installed due to the holes for 6SJ7 and 6C5 octal sockets does not exist. Also has under the chassis two 16uF 700 volt caps and one 12uF 600 volt vs standard HV caps found on 'normal' schematic. The 700 volt caps are not in parallel. Also the can capacitor has only two 10uF 450 volt, not three 10uF in can like a normal Scout 680. And, no couplates in the speech amp. Anyone have a schematic for this odd Scout?

(Sorry Pete, had to post this so I can rebuild it. No more posts beyond this subject for 30 days).

[K8DI]

Sixty seconds on Google.

http://www.radiomanual.info/schemi/Surplus_Radioamateur/Globe_Scout_680_user.pdf

The resources are out there, you’ll get better results here if you do a little research on your own first.

Ed
http://www.radiomanual.info/schemi/Surplus_Radioamateur/Globe_Scout_680_user.pdf

[n8fvj]

Sixty seconds on Google.

http://www.radiomanual.info/schemi/Surplus_Radioamateur/Globe_Scout_680_user.pdf

The resources are out there, you’ll get better results here if you do a little research on your own first.

Ed
http://www.radiomanual.info/schemi/Surplus_Radioamateur/Globe_Scout_680_user.pdf

Ed, that is not the Scout 680A with 12AX7 schematic. Your post has a 6U8 speech amp, not 12AX7. I searched the Scout 680 schematic on the internet, no Scout 680 with 12AX7 speech amp schematic found.

[K8DI]

You’re right it has a 6U8. That’s what the manual says. Same for the 680-A. Carefully check to see if the one you have shows signs of rework or just has the wrong tube in the socket. Trace and draw the schematic of what you have. Post it here. I’d be willing to bet what you have is not a stone-stock 680 but either a modified radio or something else entirely. 

Ed

[n8fvj]

You’re right it has a 6U8. That’s what the manual says. Same for the 680-A. Carefully check to see if the one you have shows signs of rework or just has the wrong tube in the socket. Trace and draw the schematic of what you have. Post it here. I’d be willing to bet what you have is not a stone-stock 680 but either a modified radio or something else entirely.  

Ed

This Globe 680A is an odd ball. It is factory stock as if modified the older two octal tube socket holes would have been in the chassis. No holes in chassis and has a 12AX7 in-between the older speech amp tubes. Also, way different HV capacitor scheme and the HV capacitors are paper covered or old as dirt (original). Plus, no couplates like the older 680 Scout.

[Pete, WA2CWA]

Does your transmitter cover 160 to 10 meters or does it cover 80 to 6 meters?

[n8fvj]

Does your transmitter cover 160 to 10 meters or does it cover 80 to 6 meters?

80 to 6 meters.

[Pete, WA2CWA]

In checking multiple original manuals I have for the 680 and 680A:
Both transmitters use the same tube lineup for the modulator 6U8 driving the 6L6. On section of the 6U8 is the speech amplifier, the other section is the driver for the 6L6.

Both transmitters in their original form used the PC-81 and PC-91 Couplates. However, from info I've read and heard (take that for what it's worth), original couplates have a life expectancy of approximately 30 to 40 years or earlier before internal values tend to deteriorate or fail. Since it not easy to find these couplates on the market, it's easier just to rebuild them with discreet components. Internal info on internal values of these couplates is available on the web.
 
OR the previous owner just desired not to use these RC networks and just direct coupled between stages.It's also very easy to replace the 6U8 with a 12AX7 with some minor circuit adjustments and have a triode speech amplifier driving another triode and this triode driving the 6L6.

The only Globe Scout that used the 6SJ7 as a speech amplifier driving a 6C5 triode which in turn drives the 6L6 is the Scout 65A.

The Globe Scout 66 also uses the 6U8 driving the 6L6.

All four Globe Scouts use the PC-81 and PC-91 Couplates.

There no data that I can find to support that Globe ever in manufacturing changed the 6U8 to a 12AX7.

Given the Globe Scout 680A was offered for sale from 1958 to 1959, which is over 60 years ago. How many different hands has it passed through and/or how many different circuit massages has it gone through can lead to many differences from the original manufactures design intent.