The beauty of Bogen

[love pa amps]

I will definitely work on that, it may take a while but I won't forget, most of my tube audio is on a long shelf 2 rows deep behind another set of rolling shelves, turns out it wasn't the greatest way of organizing equip

the picture I posted is somewhat of an example, I can see that equip but I can't get near it yet.....

 

[stormking]

No hurry, would love to see em.

 

[doctor fuse]

I have had quite a few Bogen amps and receivers and all have been surprisingly good quality and performance.

Here is an AP-200 integrated (7355 tubes):

SRB-20 receiver (6BM8 tubes):

RP-200 Receiver (EL84/6BQ5 tubes):

Plus many other K and M series PA amps.

Dual MO-100A amps (each 100W, 8417 tubes):

Hey Tinkerbelle! I just bought an SRB20 and have started recapping it (the 20mfd 250vdc cap replaced with a Rubycon 22uF 450vdc aluminum cap). It sounds great so far but there is a channel imbalance so I am going to keep recapping the power filter and signal coupling caps. This toob noob is looking for any advice (which caps to replace with, where to order in Canada, etc).

 

[gadget73]

Flip the mode switch from Stereo to Stereo Reverse an let me know if the low channel swaps to the other side.

 

[doctor fuse]

Quieter channel swaps to the other side when I set to stereo reverse. I have switched tubes with no change. Tried cleaning pots and switches with 99% isopropyl but no go.

 

[gadget73]

ok so the problem is upstream of that switch. What about if you jumper the two tape output jacks together, does it end up equal at that point?

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Sams if anyone is curious

this is the relevant bit of the schematic.



red dot is where the tape output feed goes. Thinking if it does not become equal with those jumped together, the problem is somewhere between that point and the wiper of the volume pot. If it does become equal, then the problem is further upstream. Wiper of the volume pot goes to the mode selector, and since the stereo reverse changed the quiet side, the signal going into the selector is not equal.

basically trying to do some relatively low effort isolation here to narrow down the problem area.

 

[doctor fuse]

I haven't tried the jumper trick yet, but I've replaced the caps circled in red (some were crumbling) and the issues of channel imbalance and a tiny soft hum remain. It's a very nice sounding receiver so I would like to improve these two issues (not sure it will ever be silent and free of all hum). I will try adding a jumper soon.

 

[doctor fuse]

Some photos of the recapped Bogen. I also gave all pots and switches a good clean and now channel imbalance is gone and hum is very minimal (probably as good as it gets).



After the recap:


Before the recap: