ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi,
just working on my BM8000 after its tuner started behaving erratically.
here is what was happening:
started perfectly normal with all preset stations in place and playing well.
After some time playing the frequency suddenly changed wildly all over the place...
now I red through various posts on the forum and things pointed to the prescaler chip which I
decided to replace on a socket.
now again all preset station are present as programmed, no frequency hopping but .....
NO audio from the tuner to be heard - all other inputs (TP1/2 PH) performing as they should.
I have checked all connections for a loose plug...nothing suspicious.
I noticed with some posts there was talk of another tuner-output involved IC 9IC8 HEF 4013 ?!
But this one sits before the prescaler chip and as the frequency can be changed without problems
that one should not be in the mix ?!
naturally I checked all plugs on the tuner boards incl the aerial plug - having said this I must mention
no external aerial was ever connected as the tuner is quite strong pulling in all local stations beautifully.
the audio switch works going through all inputs .
could someone help with a pointer ?
thank you 🤗🙏
ALF
Hi Alf
First question: Is the tuner set to automatic tuning or manual tuning?
In automatic mode the tuner is muting when no station is present.
Please try to measure the tuning voltage at P 6 PIN 2, the plug between tunerbord 1 and 2.
Should be between 3,7 and 19,5 Volt depending on the frequency.
If there is no tuningvoltage ( like I had this case ) check if the 55 Volt at P 8 PIN 4 on board 2 is present.
Without this 55 volt there is no tuningvoltage or fixed to around 1,5 Volts ).
This 55 volts come from the 180 Ohm resistor which is soldered to the big rectifier on the right side of the amp.
In my case the resistor had a broken leg. Hard to find because the preowner decided to put some shrinkingtube around the resistor for protection.
The frequency from IC 8 on PCB 9 to input of the uPC at Pin 21 should be from 384 to 464 kHz for e.g.
107.9 MHz + 10,7 MHz = 118,6 MHz / 256 = 463 MHz
Finaly keep your mobilephone away from BM 6000 and BM 8000 because the displayed frequency will hop and jump while the mobile is connected to the internet, the HF screening is made in the 80th ;-))
Hope to bring you one step further.
Best regards
Chrischi
Did you get any further?
Hello again,
yes I did indeed, not entirely sure though whether there are more issues ?
as it looked there was one of the wires plugging in on the side of the tone and filter board, touching where it wasn't suppose to touch.
that restored the tuner settings. i also checked the tuning voltage, showing at around 4mV. i readjusted that to the required 3mV but will revisit that adjustment to verify nothing has gone astray.
right now the tuning wheel won't change the frequency which could be the assembly that sits on the tuning wheel itself, slipt off perhaps ?
was just busy with a couple of other duties. - will report back, but for now I am happy that all the 4 progammed stations coming on 🙏 again.
Good to here that you got a step forward.
Of course the rotary encoder should be in place on the tuningwheel.
You wrote that you readjusted the tunungvoltage to 3 mV?
Please clarify where you measured the 4mV in the tunersection.
I see in the manual that the tuningvoltage should be between 3,7 and 19,5 Volt !!??
Hello Chrischi,
if you look at section 6-2 in the SM under 'tuning voltag' you will find "........connect DC voltmeter to 2TP21 and adjust 2R2 to 3.0V"
all working (for now), it was the little pcb that sits on top of the tuning wheel - it slipped off when I closed the front panel.....
so, all good 🙏🤙🤗
Aha🤔
Adjusted to 3 V not to 3 mV, that makes Sense.
Stay tuned😁👍👍
🙄
these bloody typos !!
sorry about the confusion