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Message |
    
Ou812
New member
Username: Ou812
Post Number: 3
Registered: 11-2006
| | Posted on Sunday, November 19, 2006 - 11:39 pm: | 
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I have a Mckinley with weak transmit and no or weak modulation. (Self inflicted).
Swapped mics no change.
PA speaker squeals when keyed even with volume turned all the way down.
External Watt meter AM shows about 3 watts.
External Mod meter will full calibrate but no swing on AM
External SWR about 1.5:1
USB and LSB will swing about 1/2 watt and swing mod to about 40-50 percent.
SWR meter will go forward slightly with mod applied on USB / LSB.
Driver and Final are new NTE 235 and NTE 236.
TP8 will not drop below 56mA and
TP7 barely gets down to 35mA.
I am using the SAMS for a Cobra 142/140 GTL .
This radio I got used and although it was beat up it worked real well. I cut R104 for the mod
then started peaking the coils L26,L27,L28,L29 when I came up on L36 something snapped it lost carrier. Now has the new final and driver and after tuning VR6,VR7,VR8,VR9 and the L's I have 3 watts out and no Mod on AM.
IC5 MB3756 previously tested with no voltage at pin 8 but now seems fine with 8.2 on tx?
I am wanting to replace the IC4 TA 7222P as it shows 2.9v on Rx and 2.6v on Tx but I have read on this forum simular probs with bad caps will blow out the chip again. What caps should be replaced as well? |
Ou812
New member
Username: Ou812
Post Number: 4
Registered: 11-2006
| | Posted on Monday, November 20, 2006 - 1:12 am: |
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Mis information update: PA speaker works fine with Audio. Trying to find TA7222P with out high min order. Is a NTE1278 ok quality? |
Ou812
New member
Username: Ou812
Post Number: 5
Registered: 11-2006
| | Posted on Monday, November 20, 2006 - 1:18 am: |
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IC4 TA7222P PIN #9 with 2.9v Rx and 2.6v in Tx. What caps to replace along with it? |
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