Recapped a 3903-su and a 4989dg,as well as filter caps.I racapped the 8uf with 10's and the 16uf with 22uf @450.I have checked the rest of the caps and are not shorted but will change them after I get the present problem fixed.
The problem I have now is it only hears the one local station but is very distorted.
The voltages on the
6A7 plate 256vdc,G3&5 115vdc,G2 200vdc,G1 -16vdc
78 plate 300vdc, G2 117.5vdc,G3 -4.9vdc
75 plate 251 vdc, PD2 -4.3vdc, PD1 -6.2 vdc
42 plate 292vdc, G2 298vdc, G1 -16vdc
80 313 vdc
I have checked my wiring several times thinking i may have made an error some where can't seem to get things running smooth here, any suggestions? I have checked the tubes on the old Precision TT.
Any help would be appreciated
Thanks Martin.............
:Recapped a 3903-su and a 4989dg,as well as filter caps.I racapped the 8uf with 10's and the 16uf with 22uf @450.I have checked the rest of the caps and are not shorted but will change them after I get the present problem fixed.
:The problem I have now is it only hears the one local station but is very distorted.
:The voltages on the
: 6A7 plate 256vdc,G3&5 115vdc,G2 200vdc,G1 -16vdc
: 78 plate 300vdc, G2 117.5vdc,G3 -4.9vdc
: 75 plate 251 vdc, PD2 -4.3vdc, PD1 -6.2 vdc
: 42 plate 292vdc, G2 298vdc, G1 -16vdc
: 80 313 vdc
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:I have checked my wiring several times thinking i may have made an error some where can't seem to get things running smooth here, any suggestions? I have checked the tubes on the old Precision TT.
:Any help would be appreciated
:Thanks Martin.............
:
:
Thanks for posting your tube pin voltages. Always a good first step. Your antenna coil may be open or the bandswitch is making poor contact. See if the radio works if the a long is connected to the grid cap of the 6A7. This bypasses the antenna path. The G3 voltage on the 78 tube should zero. Richard
http://www.oldradiosrus.com/build.html
cathodes are all grounded and neg voltages on grids.
I checked the ant coil through ,all resistances check ok with continuity end to end. Tried the ant wire to grid cap of 6a7, station is there but very distorted and weak. Still wondering about dc voltages with the new higher value electrolytics.
Thanks martin..........
We're only wanting some degree of capacitance coupling here. In the case of the small chance that the monitor should be affected in the SAME mannner, walk the test clip connection from those det plates, forward to the plate of the IF amp . . . reevaluate . . .then to the 1st grid of the IF amp . . .reevaluate . . . and then finally the plate of the 6A7 mixer-up-us. Standing by . . . |
:I should have mentioned the correct schematic for this 610 was on Philco page7-87 2nd type schematic (http://www.nostalgiaair.org/Resources/797/M0013797.htm) :cathodes are all grounded and neg voltages on grids.
:I checked the ant coil through ,all resistances check ok with continuity end to end. Tried the ant wire to grid cap of 6a7, station is there but very distorted and weak. Still wondering about dc voltages with the new higher value electrolytics.
:Thanks martin..........
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: : : :  : : : : : : : : :Sir Martin. . . . . : : :Postus errata . . .? . . . as per your . . . : : : : :78 plate 300vdc, G2 117.5vdc,G3 -4.9vdc : . . . . . . and your sets grounded G3 is really G1 . . . right ? : : : :Phase 1: : : : :All of the screen voltages are excessively high, check out the presence and tolerances of the cluster of voltage divider resistors: : : :Resistor items: : : :#39----10K . . . . . #40----25K . . . . . #38----50K . . . . . #42----32K : : : :Phase 2: : : : :You are one up on me already, on my initial thought of having you take a bit of antenna wires input, into the grid cap of the 6A7. : : :Sooooooo . . . get out one each port-a-bubble pocket transistor AM radio . . . or a small table model radio. : : :Best connection access . . . if ye olde Peel-co chasis is being placed on its side now. : : :Use a test lead with its end alligator clips . . or 2 . . or 3 daisy chained, as per the sets proximity requirement. : : :(Best . . vewy . .vewy . . . close to each other.) : : :One clip end goes to the diode plates of the 75 and then the end of the required clip lead length(s) is wound 1 turn around the monitoring receiver, with that alligator end merely clipping onto the leads central insulated wire. : :We're only wanting some degree of capacitance coupling here. : : :Fire up ye olde 610 and get it "doin its thang" on that sole . . . poorly received, colloqial, local, yokel station, and then bring down its volume to the extent that you can then concentrate on the monitor receivers audio and then tune that monitor set to the second "harmonica" . . .of 920 kill-o-hurts . . . and expect that prior received station to additionally be coming in on that second set. : : :Its a miracle . . .ITS A MIRACLE ! . . . . . now make an evaluation of that sets received audio, is it having the same fallacy as the Peelco was ? : : :If not, one needs to look towards the suspicion of the Philco sets fault being in the Det-1stAF-AVC or AF output stages. : : : :In the case of the small chance that the monitor should be affected in the SAME mannner, walk the test clip connection from those det plates, forward to the plate of the IF amp . . . reevaluate . . .then to the 1st grid of the IF amp . . .reevaluate . . . and then finally the plate of the 6A7 mixer-up-us. : : :Be fully expecting progressively less gain per forward stage connection, and make up with it via the monitors volume adjustment. : : :Wherever your distortion clears up . . . .you have then found the sets fault . . . with it being downstream, circuitry wise, from that point. : : : :Standing by . . . : : : : : :73's de Edd : : :  : |
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::I should have mentioned the correct schematic for this 610 was on Philco page7-87 2nd type schematic (http://www.nostalgiaair.org/Resources/797/M0013797.htm)
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::cathodes are all grounded and neg voltages on grids.
::I checked the ant coil through ,all resistances check ok with continuity end to end. Tried the ant wire to grid cap of 6a7, station is there but very distorted and weak. Still wondering about dc voltages with the new higher value electrolytics.
::Thanks martin..........
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Your question abt. G3 on 78, it is tied to neg voltage.
voltages now are
6a7- pin2 204v,pin3 105v,pin4 188v,pin5 -2.5v,grid cap -2.1v
78- pin2 239v,pin3 105v,pin4 -2.1v,grid cap -2.1v
75- pin2 215v, pin3 0v,pin4 -2.2v,grid cap -1.7v
42- pin2 246v,pin3 241v,pin4 -3.5v
Thanks Martin.....
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:Thanks for your reply Edd, good tip with second receiver.There was no distortion,so figured out it was a bad 42 tube. oops missed a bad r38 had doubled in value, also a leaky c47, also didn't have chassis grounded. Now we have weak audio but distortion has disappeared. Maybe an alignment? or another weak tube but they all checked ok.
:Your question abt. G3 on 78, it is tied to neg voltage.
:voltages now are
:6a7- pin2 204v,pin3 105v,pin4 188v,pin5 -2.5v,grid cap -2.1v
:78- pin2 239v,pin3 105v,pin4 -2.1v,grid cap -2.1v
:75- pin2 215v, pin3 0v,pin4 -2.2v,grid cap -1.7v
:42- pin2 246v,pin3 241v,pin4 -3.5v
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:Thanks Martin.....
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Martin...................
Sir Martin. . . . .
The one section that PULLS any appreciable power and thus mainly loads down the power supply of the set is your AF output stage.
Consult the schema markup and note that within the YELLOW highlighting, is a designated basic series voltage divider, made up of 3 resistors and their feeder branch offs.
Do see that the centertap of the HV secondary winding has to pass over to the right and thru three divider resistors, before it EVENTUALLY gets grounded . . . to the far right.
The negative voltages developed at those three node points are further distributed to the circuitry by the
branches designated by the PALE ORANGE (Audio) and PALE GREEN (D-AVC)feeder resistors.
Be sure that all resistors asssociated with that marked up circuitry are O.K. on their specs.
If the bias reaching the 42 is in error (more negative in value) , it can cause less than normal current consumption . . . . higher B+ . . . and a shift of the A.F. stages class of operation.
If it has . . . forbid . . . shifted progressively towards the direction of class C operation . . the power supply current consumption decreases and the tips of the produced peak audio nodes are being clipped.
REFERENCING:
73's de Edd
:Normally when trouble shooting, high plate voltage indicates low or lack of conduction of the tubes. (No Gain). One place to start is the ground points. A lot of times components share the same grounding points. Check all grounds.
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Martin........
:Martin........
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Finally got it figured out , replaced all riveted grounds on tube sockets with star washers and screws and the reworked the ground for the negative bias resistor.Got a very nice sounding old radio to listen to now.
Thanks martin...........