Those are okay.
If you don¡¯t have extra tubes, try swapping around the 12BA6¡¯s and see if anything changes. ?Also look at the AGC circuit and make sure that the transistor (can¡¯t remember if it¡¯s Q4 or Q7 but it¡¯s the one that generates the AGC voltage) is a 2N3877 or equivalent.
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Tue, Mar 5, 2024 at 5:01 AM, Michael Jensen <
kavigal@...> wrote:
Okay they resistors measure as follows:
Both liftet from PCB
R41=837 OHMS
R89=557 OHMS
So not horrible out of tolerances I guess.
On Mon, Mar 4, 2024 at 11:43?PM Steve Wedge, W1ES/4 via <w1es=
[email protected]> wrote:
Those figures don't indicate a problem. Ideally, TP2, with the preselector detuned, should read -1.35V Your reading isn't terrible. So now we need to see why you're getting S5 with no signal. On the schematic, R41 and R89, in the meter bridge circuit, should be checked.
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
Sent with secure email.
On Monday, March 4th, 2024 at 3:53 PM, Michael Jensen <
kavigal@...> wrote:
@Steve Tonight's numbers :).
Cold and detuned TP2=-1.335v
30 mins TP2=-1.267v
60 mins TP2=-1.259v
I get your point about "
The important part here is if the voltage at TP2 with respect to time."
Now what is the verdict? Too much voltage drop? What do you think?
Thanks, Michael.
On Sun, Mar 3, 2024 at 11:49?PM Steve Wedge, W1ES/4 via <w1es=
[email protected]> wrote:
Resistance is the most important here.
We now need to measure the TP2 voltage from startup to a point long after warmup. If this value drifts towards 0V then there is a chance that you have a gassy tube.
The important part here is if the voltage at TP2 with respect to time.
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
Sent with secure email.
On Sunday, March 3rd, 2024 at 12:50 PM, Michael Jensen <
kavigal@...> wrote:
HI again!
Tak for linked Glenn, kunne godt minde lidt om mit problem :).
Okay enough "Danglish" ..
@Steve, Thanks for taking your time to reply!
Detuned and with AVC ON, TP2 voltage is-1.26, right now, I did an adjustment cold, so seems to have dropped ever so slightly after proper warm up.
RF GAIN Pot measures ~12Ohms(seem to be some capacitance) with wires attached, so guess that is quite okay.
Thanks, Michael-oz8abr
On Sun, Mar 3, 2024 at 2:11?PM Steve Wedge, W1ES/4 via <w1es=
[email protected]> wrote:
Michael, what is the voltage at TP2? There are other resistors in the bridge circuit and I have seen them go out of tolerance.
What is the resistance reading across the RF GAIN pot?
73,
Steve Wedge, W1ES/4
Time flies like an arrow. Fruit flies like a banana.
On Sun, Mar 3, 2024 at 07:09, Glenn, OZ1HFT <
glenn.mh.dk@...> wrote:
Hi Michael
See this thread:
/g/DRAKE-RADIO/topic/r_4b_agc_issues_part_trois/103544827
--
best regards,
Glenn, OZ1HFT
