Search results

Thanks - this is really useful - will explore. From the schematic I have it looks as if the dc line derives from a 50V tap on the mains transformer rectified with a diode IN4007 then smoothed with electrolytic and tantalum filter and two zeners dropping the dc to 24V. I think I found the...

Thanks - it doesn't seem to be M1 or M4 FETs - both test ok. No signal appears at V7 and no sound at all from speaker. Not sure where else to look ?

Use an ir cam / phone to look for hot spots to give a probable location for over current - could be ageing cap .

A learning curve. We’ve all made these mistakes , hopefully only once along the way. Great that it seems a simple fix.

Latest - amp worked fine after installing IN5392’s and replacing 12V regulater. Then the valve rectifier failed and was replaced after which one of the 6L6 power tubes failed short circuit. I replaced all 4 with matched set but now no sound, again! 12V supply is the and fan is running but...

I‘d Chechen the speaker and leads to it - use a low voltage battery 9V to make sure it pops. After that check the AC mains input to the rectifier then dc high voltage on the capacitor board then at the anodes of each valve. Boogie transformers are pretty strong so failure is unlikely unless it’s...

Thanks, that’s useful and understandable. Would not wish to upset the careful planning implicit in the design.

I’m wondering about using a GZ34 as a sub. Will its heater current draw be too much for the mains transformer? Otherwise it seems a better tube.

My Mk5 90 v2 has a 5U4 - can I substitute a GZ34 or is the heater draw too much for the mains transformer?

Success !!!! I sourced alternative to the suggested replacement for the IN4007 (IN 5392 which are said to be obsolete). Installed these yesterday and to my delight I now have signal from input to anodes of V7 so assume this will now drive the power valves - final tests this weekend but expect...

I've found an equivalent to the IN5292 and am in the process of installing the replacements. Will report back on the result ! Thanks for the comment. Steve

:my mk5 90 12v supply failed when switched on after a long rest during covid pandemic.1N4007 diodes and 12V regulator needed replacing. After that heater supply returned but no drive t v7 grids. Tried replacingJ175 M1 and M4 without improvement. Boogie suggests using 1N5392 diodes instead of...

You can do as suggested on the V5 90 head. I remove the chassis to work but that’s probably overkill. These ‘Swiss Army’ amps are over complicated and unnecessarily complicated to service, especially in the field. I think this a result of hiding assembly cost and passing it downstream...

Thanks, plenty to explore here will proceed tomorrow and report results !

Will do as suggested and report back. Thanks, Steve

Can't see anything on grid of V6A - fan is clearly running now.

Apologies for the delayed reply - hospital duties for family making life errratic. The cooling fan is running so voltage regulator must be ok now. If I inject a signal at the input I can find it on pin 2 of V5. Not sure which of the J175's to check or exactly how ! Possibly a failure there...

I did check and replace the Voltage regulator, which brought the rectified heater and 12V supply back but signal seems to disappear between V3 and V7 (nothing at the grids of V7). I guess it may be failure of J175 but which one - how to check ?

I seem to have a similar problem - amp left unused for the duration of the pandemic. When switched on after that all the diodes in the 12V heater supply failed. I replaced these but the amp signal does not get as far as V7 - could this be failed J175's ?