# Benson Monarch Reverb inspection



## Alan Small (Dec 30, 2019)

I made a house call to a friend today who owns a Benson Monarch Reverb which stopped working.

Very neat and tidy wiring.

A power tube had shorted which caused the first dropping resistor to fail: new 1k- 5 watt installed and new matched pair of jj 6v6 (tubestore.com matched '26')

A happy amp again😁

I will be making drawings of this amp from photos taken on site.






































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## SpinalTipp (Jun 13, 2017)

Thanks for the save Alan!! Can't tell you how much I appreciate the house call to get her back in shape so quickly and to teach me a few things along the way. Enjoy the cab (and the cookies)!


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## Alan Small (Dec 30, 2019)

Ginger Molasses Cookies, 6pc (Nicholyn Farms) | Nicholyn Farms


Family recipes that have been perfected through generations of taste testing!



nicholyn.com





Any travellers near Barrie...a wee bit WestNW is a nice farm store with super delicious ginger cookies


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## Scottone (Feb 10, 2006)

thanks for sharing Alan. I have my Tall Bird reverb unit apart as well so will snap some pics if anybody is interested


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## Alan Small (Dec 30, 2019)

Scottone said:


> thanks for sharing Alan. I have my Tall Bird reverb unit apart as well so will snap some pics if anybody is interested


Yes please do share. Thank you


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## hoodnight (2 mo ago)

Hi Alan, did you happen to keep a record of what filter caps were in there? I've got a schematic almost finished but the filter values are the only thing I can't track down.


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## Alan Small (Dec 30, 2019)

I dropped the ball on that plan🤪

The two f&t cans were 32/32- 500 each

The first stand alone 47-500(by its size..i didnt make a note) removed some ripple before entering the first can which half of fed the output tranny ct and then the second half fed the screens before heading to the second can for feeding the pi and reverb and the final half can for the preamp triodes


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## hoodnight (2 mo ago)

Alan Small said:


> I dropped the ball on that plan🤪
> 
> The two f&t cans were 32/32- 500 each


 Absolute legend! I thought it had to be 32/32. Chris Benson dropped in to the thread on ampgarage and said they were using 22/47/22/22μF. I assumed he was using two 22/22μF cans with another 22μF in parallel with one half of a can to make 44μF and he'd just rounded them to standard values, but I realised F&T don't make 22/22's!

Do you possibly recall what the parallel cap and the reverb filter cap values were? My assumption is 32 plates/32+10 screens/32 PI/32 preamp/22 reverb?


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## Alan Small (Dec 30, 2019)

hoodnight said:


> Absolute legend! I thought it had to be 32/32. Chris Benson dropped in to the thread on ampgarage and said they were using 22/47/22/22μF. I assumed he was using two 22/22μF cans with another 22μF in parallel with one half of a can to make 44μF and he'd just rounded them to standard values, but I realised F&T don't make 22/22's!
> 
> Do you possibly recall what the parallel cap and the reverb filter cap values were? My assumption is 32 plates/32+10 screens/32 PI/32 preamp/22 reverb?


What i recall...see drawing


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## hoodnight (2 mo ago)

Ah OK, interesting. I'm working with this model below:










It seems to align with his "small reservoir into large screen", and also with his comments about being inspired by old Supro's - the Thunderbolt had paralleled caps on the screen node as well. 










Also note in your photos the filter capacitor on the first tag strip from the input jack - looks like the reverb driver is fed off of this, and then the recovery plate is fed off of a 470K resistor from the driver's plate feed.

I may have been a little obsessive about nailing this circuit over the past month or so...


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## Alan Small (Dec 30, 2019)

Good research on your part and the b+ supplies are similar and will work just fine...we are not certain the unit I worked on was original or not...you may have other interior pics which can confirm...

Chris was open and revealing during his participation in THE TRUTH ABOUT VINTAGE AMPS podcasts and he is scheduled to talk again soon...very cool podcast


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