Blaupunkt Arkansas 43942 Restoration

[Darrencambs]

Ok. I’ve put the ECL86 valves back in and powered up. Each are negative 0.9v on pin 1 and just under +5v on pin 7. Both of them are glowing.

Current reading has jumped up to about 260mA whereas it was only 150mA with the valves out. I’ve switched off for now just in case. Should I be concerned about anything?

[ms660]

Cathode voltages looks ok to me....do the Ohms law....I = V/R, if the cathode resistors are within spec then that means approx 33mA flowing through each valve which is well within their limits.

Lawrence.

[Darrencambs]

Thanks Lawrence.

I hadn’t checked those resistors. Probably should have done..!

I’ve switched back on and everything seems stable after 30 mins or so. I’m going to put everything back together now and see whether we have sound....

[Darrencambs]

Good news! We have music!

Had it running for a few hours now without any major issues. Good VHF and MW reception. No nasty buzzing sounds or distortion.

Volume on the left channel is stronger than right though, so that's going to need further investigation. I swapped the ECL86s over, but it's still stronger on the left.

The autochanger has life in it too, but I'll take that out and refurb it over the next few weeks.

Thanks again to everyone who's contributed to this thread.

[ms660]

Originally Posted by Darrencambs

Volume on the left channel is stronger than right though, so that's going to need further investigation. I swapped the ECL86s over, but it's still stronger on the left.

A couple of quick things that might be worth doing is to check the anode voltage of both triode sections of the ECL86's, they should both be the same within reason and should be near enough to the voltage given in the schematic, if they are noticeably out then check the value of the anode load resistors, the other thing worth checking is the cathode bypass capacitor, that's the electrolytic capacitor that's connected across the cathode resistor (C750 or C760 on the appropriate channel) if that has lost it's capacitance negative feedback will occur which will reduce the sound output on the corresponding channel, you can bridge the old one in circuit with a good one of similar value just to try it (observing the polarity) Personally I would replace both of them anyways, along with the electrolytic that's across the FM discriminator diode circuit (C743....2uF)

Lawrence.