Can't find switch

[Joe Miller]

Still working on my AW23.  I can't seem to find the "radio/phono" switch on the set.  The switch shows as  a double pole sw on the schematic-- to remove the radio audio and insert the phono audio.  I also have a spare parts AW chassis.  I've traced the wiring from the phono post on both sets and it goes to the audio section (different sections I might add) but there is no switch? 

 

Anyone know where this switch is located?

[Thomas Day]

Joe:

This is one of the apparent differences between the early 5 knob and later 7 knob series. There is no switch on the 5 knob chassis, at least not on mine. There are no directions in the documentation I have on using the phono input on the early version of this  radio, but there must be in the documentation for the 5 knob chassis.

Thom

[Y2K Bruce]

WOW-I never noticed this difference but I just looked at my 5 knob sets and I just read all the 5 knob documents and indeed there is no mention how to operate the Phono, except there is discussion on using a transformer if the RP is not an original from Scott.

You are supposed to run a jumper wire between the 2 RP posts if not using an RP but thats my limit of knowledge.

On the 7 knob versions, one of the small knobs is a phono/radio control.

[Joe Miller]

Here's what I've learned:

• My phono is indeed the one shown schematically in the AW23 Technical brochure that Kent sent me last week.  Bruce you are right in that when the phono switch (on the phono) is not in the phono position it shorts (jumpers) the phono an ground posts together. 
• On the Parts AW23 chassis the phono post is connected to the 1st audio cathode which is grounded??
• On my good AW23 chassis the phono post is connected to the cathode of the tuning meter amp?  That doesn't make any sense to me.

I'm really baffled on this given that two separate chasses are wired differently and neither seem to make sense as far as presenting a phono signal to the amp and removing the radio signal at the same time. 

I must be using the schematic for the 7 tubes AW23.  Does anyone have a schematic for the 5 knob version?

Has anyone ever successfully played a phono on the 5 knob set?

Serial numbers are Parts chassis Z-379 and good chassis Z-252

Need some help on this one.

Thanks,

Joe

 

[Norman S Braithwaite]

Apparently the service manual showing the schematic of the 5-knob version is very uncommon.  I have a copy and can scan and post the schematic when I have access to my scanner in a couple days.

Norman

[David C. Poland]

Starting with the 7 knob AW-23 and all subsequent models there was either a radio/phono switch or a position on the wave change switch for phono.  But on the early AW-23 (5 knob set) , the previous Fifteen, 12 tube Allwave Deluxe,  2-dial and AC-10 models there was no phono switch. Rather, the "switch" is the jumper wire from the phono post to ground. The jumper wire has to be there for the earlier model radios to play. (The jumper grounds the cathode of the 2nd detector or of the first audio amp stage depending on the model.)

The earlier models, up to the early AW-23  5 knob, injected the phono signal into a cathode circuit, by  substituting the phono wires for the jumper wire across the ground and phono posts.  The phono also needs a switch to short the phono wires so the radio would play. To avoid traces of the radio signal when using the phono, be sure it is tuned to a quiet spot on the dial or turn the wave change switch midway between 2 bands to quiet the radio circuits.  In addition, the phono should have its own volume control.

For the early AW-23, the phono MUST have its own volume control lest you blast at full volume because the phono signal is injected AFTER the radio's volume control. Turn the radio volume and sensitivity controls to minimum to prevent radio signals while using phono input.  However, the tone controls (bass and treble) are fully effective with  phono input. 

So, to use a CD player, IPOD  or FM tuner ...  remove the jumper across the phono and ground post and use the posts to connect the device. Arrange a switch to "short" the 2 leads when you want the radio to play. The phonos Scott supplied had a phono/radio switch and also a volume control.  I regularly use a CD player on my AW-23 - it sounds great and tremendous volume is available.      

Also, Radio Shack carries a stereo "closed circuit" mini jack that can be wired to make the jumper connection until you insert the stereo mini plug of the patch cord of your CD player or IPOD.

[Joe Miller]

Norman,

Thanks for offering to do this.  I am in real need of an accurate schematic for the 5 knob set.  I have an AW23 Parts Chassis that I am using as a wiring reference and my good one that I am going through right now.  Both have 5 knobs.

My good one was playing fine, but I opened it up to verify that it had been recapped and to address a known wiring problem (the previous recapper connected a wire from the phono input to the grid of the RF amp, using the phono post as the antenna post and bypassing the antenna coils, because he couldn't find the antenna post--he is an older gentleman)

I have found a number of puzzling wiring anomalies in my good set.  Please note the three questionable areas on the attached picture. 

The larger red circle is the most concerning to me.  The leads from the transformer which is mounted under one of the cans on the top of the chassis have been cut and taped.  I think this is the coupling transformer between the 1st AF and the 2nd AF push pull 6C6's but not sure yet.  Obviously something else must have been done to the set to enable it to play without this transformer connected.

The green rectangle identifes a newly added red wire that doesn't exist in the parts chassis.  Hopefully the schematic you post will shed some light on what is going on.

Finally the smaller red ellipse in the upper right hand corner identifies where the phono connection terminates--it appears to be injecting at the cathode of the tuning meter amp (76 tube).  But when the phono is not in use and the radio is playing, this point is to be grounded which would disable the tuning meter. BTW the parts chassis phono wiring terminates at the cathode of the 1st AF 76 tube, but the cathode is grounded so the phono couldn't work when connected. So the wiring between the 2 chasses even differ.

So, I don't plan to make any changes until I can get my hands on a accurate schematic.

Any thoughts on this is appreciated.

[Joe Miller]

Here's the right picture

[Joe Miller]

Sorry,  having trouble with editing pictures

[Joe Miller]

David,

Thanks for your comments.

As you can see in the above thread, both of the AW23 chasses I have use different connections for the phono input.  Once I figure this out, I will use your idea on connecting an IPOD to it too.

Do you know where your phono input connects (injects) at?

Thanks

Joe

[Joe Miller]

I'm going out on a limb here, but I took a look at my good chassis and it looks like the disconnected leads do belong to the coupling transformer between the 1st AF and the 2nd AF.

Further, the 1st AF tube circuit has been modified to add resistance in the cathode leg and the screens and plate have been tied together.  Additionally, it looks like the plate is now capacitively coupled somehow to the next stage (not for sure yet).  The set did play so this reconfiguration must work, but given the extent of the mod, it could have been done as a factory mod?  Is there a source that lists all the factory mods done to All-Waves?

Hopefully Norman's schematic will shed some light on this mystery.

Joe
 

 

[Norman S Braithwaite]

Joe:

I'm back in town and will scan and post the schematic this afternoon if I remember to pick up the service manual during lunch.  The transformer has been disconnected probably due to an open winding.  The push-pull 6C6G audio driver tubes that were once fed by the transformer have been rewired to operate as a phase splitter and audio driver stage.

Norman

[Joe Miller]

Norman,

Thanks for everything.  I also noticed that the transformer in my parts chassis also has an open winding.  Was that a common problem?

Do you know if this was a common modification that was done to fix the transformer problem?  Does it affect output performance?

Once I get your schematic I will mark up the mod for reference.  I am also hopeful the right schematic will resolve the mystery of where to connect the phono input.  Right now it connects at at the cathode of the tuning meter amp--that doesn't seem right to me.  Will probably connect phono in put to "top of the volume control".