EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Comment by Steven Mckelvey on November 7, 2019 at 2:32am

Hi team

I have a power chassis for allwave 15 that has some mods that look factory (looking at the rivets used).

1/ A "black box" is added that is not on the riders !

2/The 2 watt resistors are subsequently rotated 90 degrees to cater for the addition.

3/The wattage of said resistors is different from riders

4/ Someone has done some repairs by adding a later 140 ohm 5 watt resistor where hook wire runs - I don't know if there was just wire there before that got hot (see my pics) or there was a previous resistor.

5/ The added black box has 3 wires - one from each 2 watt resister and a ground.

Any advice gratefully appreciated - chassis has 1930 penciled underneath. 

Comment by David C. Poland on November 7, 2019 at 11:06pm

Your AW-15 amp looks totally stock - except for that newer ceramic resistor you mention.

Every Scott AW-15 amp I have had has the added circuitry for the earphone jack, as does yours. But the earphone wiring is omitted from the AW-15 Amp circuit diagram. The earphone jack is wired to cut off the speaker when the earphone plug is inserted, hence all the additional wiring you see.

Not supposed to be a resistor to the center tap of that transformer secondary winding, so I would remove the ceramic resistor. Do replace the caps in the 2 metal bathtub units riveted to the chassis apron. Also, replace the 2 mfd cap in the smaller black box connected to the center tap of the 2 1/2 volt winding to the 2A3 filaments. Don't remember what is in the other smaller black box.

Notice the wire to the 110 volt primary winding appears broken off the 110 volt lug.

Good luck.

Comment by Steven Mckelvey on November 9, 2019 at 1:09am

Hi David

Thanks for responding and for the valuable feed back.  I will replace all the caps as you suggest and ditch that ceramic resister - Someone has replaced the three 8 Mfd  with stupidly high caps!  So out they will go.  Thanks for pointing out the loose wire to the 110v tap - I suspect that was deliberate as I live in New Zealand and out mains run at 220v so this radio is run with the use of a transformer.  If someone was to flip the switch on the chassis to 110v it might cause some damage even with the transformer....

Anyway thanks again.  I will be following the earlier post on the Allwave 15 restore by Jon Ketron as my blue print .

Steve

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