Beomaster 1900-2 will not go to standby

[Loddebolt]

When switching it on it goes to standby and the standby led comes on and when touching a control field it comes on and works as expected. When touching the standby field, I can hear the relay turning off but immediately turns back on again and on and off as long as i hold the standby field, when I release, the relay is on but no program is selected and no standby led. I suspect it could be the ‘switch on’ signal that switch it back on as soon as it switches off, the collector and base of ic9 measures 4.45v and 14.9v respectively (4.95 and 13.9 when touching a control field other than standby) I’ve replaced ic9 and verified all component around it. I’ve suspected ic6 to be faulty but I’ve tried swapping ic5 and ic6 but no difference. I’m just about to give up unless anyone has has a good suggestion.

[auric]

Check the transistors eg. TR22 and around the “electronic switch”, eg TR30,32 etc.

I’ve come across a few instances where that are “leaky” and need to be replaced.

You’ve also checked some of the electrolytic capacitors? Most are failing by now.

[Dillen]

Check IC9 (SPS5431).

Martin

[Loddebolt]

Thanks guys, I’ve replaced tr30, tr32 and ic9 and verified the resistors, capacitor and diode that are connected to them.  Could a ‘leaky’ tr15-tr22 cause a ‘switch on’ signal without setting the program? Do you agree that the ic9 collector voltage looks weird? The schematics says 0,8(15)v

[chartz]

For me it was TR25.

Location: Burgundy

[Dillen]

Whisch type of transistor did you fit for IC9?

All lamps working and correct wattage? – No LED “conversion”?
The three lamps illuminating the tone control dials double as bleeders for the 15V supply.
It’s not uncommon to see that these Beomasters won’t go into standby, if to many
lamps are out, wrong or replaced by LEDs.

Martin

[Loddebolt]

used bc516 for ic9, some lamps has been replaced using 12v 70mA lamps, no LEDs

[Peter Fabian]

I have a similar issue since recapping my unit. Before recapping, I did not have right channel (in either of speaker 1, 2 or headphones) but otherwise it worked fine.

Now, when I recapped it, I did, at first, blow one of the power supply filter caps (I misread the markings and connected negative to ground on both sides, oops) so there’s a chance I blew something downstream then… it doesn’t seem like the power side gets any voltage? But the control side does.

 

So what is happening now is – when I turn on the machine, it goes into standby. When I touch a program button, it does come out of standby, but no program lamp goes on. (The volume and tone/balance control lamps do all come on). I’ve replaced the blown cap with another one correctly.

The machine is not reacting to Standby switch, unless held. If held, the relay keeps switching off and on. The program lamps work fine when voltage is sent through them when disconnected from the amp.

 

Can I test these transistors in situ without desoldering them? And if needed, how do I check the IC9, other than visual damage?

[Author]

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