That's a good move! Those caps play a significant part in what's going to come out of the speaker.
Glad all is quiet and working.
No need to do anything. The MM side is ready to go.
You could add a cap in there to increase capacitance for the cart, but there's already about 150pf on the PCB.
Finally received my James transformer after a very long wait in Canadian customs/post. Tested voltages and get the following:
- Secondary 1: 9.37V / 9.37V
- Secondary 2: 175V
The BOM suggests a secondary 1 voltage of 9.5V. Is there any issue having 9.37V? I think I read somewhere that the BB3 was originally spec'ed at 9.0V so hoping it won't be an issue.
- Secondary 1: 9.37V / 9.37V
- Secondary 2: 175V
The BOM suggests a secondary 1 voltage of 9.5V. Is there any issue having 9.37V? I think I read somewhere that the BB3 was originally spec'ed at 9.0V so hoping it won't be an issue.
Purchased the O-core version. Price including shipping to Canada was $62USD. For some reason shipping to Canada from Taiwan is more expensive than Europe.
James put it together and shipped promptly but it was stuck for about a month in customs/Canada Post. It hit customs around Dec 20 though so perhaps it was just bad timing.
James put it together and shipped promptly but it was stuck for about a month in customs/Canada Post. It hit customs around Dec 20 though so perhaps it was just bad timing.
I've quoted Flikomans post as I have the same problem. The only difference was the relays weren't working either. Strangely enough I found my brand new 7805 also from Mouser was faulty. That's simple enough I thought so I changed it with a L7805CV, from Amazon, which was all I could get at short notice.
I still have the same problem, the only difference is that the relays now click when toggling to MM. LEDs do not light.
Like Flikoman, I'm getting voltage (spot on at 7v on the pc88's) on the heaters, as soon as I put a tube in, it disappears.
Help please.
The modern 7805 regulators with the very thin metal tab are somehow different to the older versions with the thick metal tab.
The new ones don't cope with the current surge on switch on when the heaters are cold and low resistance.
The preferred regulator is a Texas Instruments LM340T-5, this is available from Mouser.
The MM mode Leds next to the relays will only light when V1 is conducting so won't light if you have no heater supply.
The new ones don't cope with the current surge on switch on when the heaters are cold and low resistance.
The preferred regulator is a Texas Instruments LM340T-5, this is available from Mouser.
The MM mode Leds next to the relays will only light when V1 is conducting so won't light if you have no heater supply.
Thanks for that, I've ordered LM340T-5.
Another point is the 7805 I took out was definitely faulty, I've now replaced it twice (with the L7805's from Amazon) and both times they were showing 5 volts on the output when first powered, but dropped subsequently.
Is this typical with what happens when the units fail?
Another point is the 7805 I took out was definitely faulty, I've now replaced it twice (with the L7805's from Amazon) and both times they were showing 5 volts on the output when first powered, but dropped subsequently.
Is this typical with what happens when the units fail?
Not all 7805 are equal.
The ones linked in the BOM are good, the ones I use now are the same as the ones Alan mentioned