[Eric]

Really not sure where to start looking?

Atwater Kent 328 (early) Rider 6-18 for the schematic and 7-34 (bottom) for chassis layout. http://www.nostalgiaair.org/PagesByModel...001334.pdf

More data
Resistors
r1 3.8 (2)
r22 118 (85)
r23 215 (165)
r3 7 (5)
r21 118 (125)
r11 10 (5)
r12 9 (5)
r10 9 (5)
r16 98 (35)
r15 67 (20)
r18 18 (12)
r19 16 (15)
r6 50 (3)
r7 16 (7)

6A8
pin3 plate 310 (240)
pin4 screen 118 (80)
grid cap 3 (5)
pin6 OP 244 (185)

[Mondial]

There are two things that seem to stand out regarding your measurements. First the B+ voltage is rather high and second the voltage across R6 is abnormal.

The high B+ could be caused by a lack of load on the supply or a shorted speaker field, which normally would be dropping the voltage to the tubes at least 60 or 70 V. Check the resistance of the field winding and see what it measures. When operating, what is the voltage on each side of the field, measured to ground?

R6 is the cathode resistor for the 6K7 1st IF tube and there is no way there should be 54 V across it. It should be 1K, and with that voltage drop there would have to be 54 Ma passing through it and therefore the 6K7 tube, which is not likely. More likely R6 is bad and increases in value when it warms up. Have you tried replacing R6 as it might be the problem.

Edit- I just looked back at your previous post and saw you measured 278 V on the grid cap of the 1st IF 6K7 ??? Is that right? If so there must be a short to B+ in the 1st IF transformer or associated grid circuit, or the 6K7 has an internal short. Remove the grid cap (with the set powered down!) and then measure the voltage on the grid lead and the 6K7 cap separately to see which is supplying the HV. This might also explain why you have 54 V on the cathode resistor!

[Eric]

Replaced R6 with a 1k 1w resistor, the old one did measure 1k

Field measures 1.1k, Each side to ground 360v & 309v and 50v across the field.

The grid cap lead from the IF xformer measures 260v the cap on the 6k7 -1.6v

Bad IF can? I will attempt to disconnect and open up and see and take resistance readings. More to follow

[Eric]

The 1st IF can is good
cap lead to white 13.9ohms
cap lead to yellow 14.3
white to yellow 1
red to blue 13.4
I have .5 ohms in lead res so the numbers are pretty close also replaced the crumbly leads while I had it out.
When reattaching besides marking when I unsoldered I verified per the print and I found the white lead had been on C26 instead of C10
now I get R6 7v should be 3v not 50v
6k7 1IF cap 6v should be 1v not 250v
The radio seems to play fine I have issues with the selectivity switch which is just plan wore out but can deal with that.
Still seeing some higher voltages like 6k7RF plate 354v, 6F6 plate 390v should be 255v about 100v higher than should be.
My question is the speaker and output transformer are not original and to get to the 1100 ohms I have 350 ohm 5w resistor in series with the field coil, can I increase this to bring the voltage down?

[Mondial]

Eric, you must have some miswiring on the speaker plug. Previously you mentioned that you had 360 V on one side of the field and 309 V on the other. It looks like you are feeding the tube B+ supply voltages from the input side of the field directly from the rectifier instead of the output side. The 309 V side should connect to the B+ supply for the tubes. Then you would have only 309 V or less on the tube plates and screens.

The field coil wire not connected to the output transformer should go to the rectifier cathode. The other field wire should connect to the output transformer and the B+ line feeding the other tubes. Straighten this wiring out and I think you will have normal voltage readings.

[Eric]

I did have those leads reversed so I changed them now seeing r6 @5v was 3 but climbed to 5, also seeing 4-5v on the 6k7 grid caps is that ok? Also have to clean the vol pot very scratchy but I'm running out of time for today. Tomorrow I will take a full set of readings. Thanks for the help

[Mondial]

There should be a negative voltage on the grid cap of the 6K7. Close to zero when receiving no signal and several volts negative when tuned to a station. The negative voltage is produced by the AVC circuit, and the stronger the station the more negative it will be.

If you have a positive voltage on the grid cap, then you most likely have a bad 6K7. Considering that there was 260 V on the control grid of that tube, it is quite likely the tube has been damaged. Actually I am surprised that it still works at all !

[Eric]

Mondial,
The radio is playing great had it on for about 3 hours off and on while I made more checks. some of the readings seemed high to me but the may be all right take a look.

120v .68a
5z4
p1 366v
p2 360v
f1 412v
f2 412

6f6
plate (255) 315v
screen (255) 306
grid (4) .02 ?

6f5
plate (150) 112
grid cap (1) .01

6k7 RF
plate (255) 322
screen (80) 104
grid cap (2) 5 to -1. goes minus on station and pos off

6K7 1st IF
plate (240) 294
screen (80) 104
Grid cap (1) -1.5 goes minus on station and pos off

6k7 2nd IF
plate (250) 318
Screen (70) 96
Grid cap (5) 0 you can hear it load up when the meter lead is attached

6A8
plate (240) 295
screen (80) 104
grid cap (5) 6 to -1.9 goes minus on station and pos off
op (185) 330 (seems high?)

Have a 90v drop across the field 333v to G on the op xformer side 417 on the other

Resistors voltage drop a couple seem high (resistors check out for value)
R1 (2) 4.5
R3 (5) 7
R6 (3) 7.6
R7 (7) 7.7
R10 (5) 4.7
R11 (5) 12
R12 (5) 13
R15 (20) 69**
R16 (35) 140**
R18 (12) 20
R19 (15) 17
R21 (125) 87
R22 ( 85) 103
R23 (165) 217**

[Mondial]

Those voltage readings look much more reasonable. The B+ voltage is still a bit high, but this might be a result of todays higher line voltages. The AK schematic specifies a 110V AC line voltage, so you might want to use a bucking transformer or run the set on a variac.

It still appears that one of the 6K7's or the 6A8 is causing the positive grid bias on the AVC line. In normal operation, there should never be a positive voltage on the grid caps. The schematic voltages don't show polarity, but the 5V indicated on the 6K7 grids should be -5V, which would be typical when receiving a station.

You can disconnect one grid cap at a time and see which tube is causing the positive voltage. A gassy tube will produce a positive grid voltage and throw off the bias on all the remaining AVC controlled tubes. The positive grid bias is causing excessive plate current, which results in the higher than normal voltages across R3, R6, R10, R11 and R12.

[Eric]

changed 1 6k7 now have
grid caps tuned to station
rf -3
1st -1.2
2nd 0
6f5 -1.1
6a8 -2.1
resistors
r3 7
r6 4.4
r10 5
r11 4.4
r12 4.5
looks better but why is 2nd IF grid cap always reading 0?
resis#16 is now 128 why still high is it a problem?

[Mondial]

Second IF grid cap should always read zero volts. It is not one of the AVC controlled tubes and the grid is at DC ground potential through the IF transformer and selectivity switch. It seems that the voltage reading on the schematic for the 2nd IF grid is a typo error.

The voltage on R16 is dependent on the characteristics of the 6F5 tube and the level of power supply B+ voltage. Since your B+ is a bit high, the voltage across R16 will also be high. You can try another 6F5, but if the audio is not distorted I would leave it alone.

[Eric]

Mondial

Many thanks for your help, sometimes I do a radio and all I do is change the caps and it works but I don't learn anything. It's ones like these that I expand my knowledge base. Love this site

Eric