This 23 Ch compact is something I’ve restored recently. I have my eye out for a SBE Brute in fair condition. Hopefully I’ll restore one of those in the near future if the price is right. I have fond memories of selling many of those in our shop years ago. They were known as an effective but cheap compact alternative. Producing a $100 radio with all 23 channels was their main objective. Except for the front panel, this MARS M-336 is in every other way a rare clone of the Brute. The Royal Sound M-336 is another rare clone of the Brute. I just saw one recently on E-bay, tempting, but he wants way too much moolah. As choices were then, I believe it’s safe to say the SBE Brute was the smallest “all 23” channel compact. Being much larger, the Realistic mini 23 came in at a distant second.
This restoration was time consuming, but at least the SBE Brute has a service manual on CBtricks. As you can see some of the capacitors are packed in tight. The board is not polarity marked so extra care was needed while doing a complete re-cap. The negative side of electrolytic caps usually goes to ground, easy enough, but I noted one cap was reversed in the audio section. It didn’t look correct at first, but after verifying it in the schematic, it did show the positive side indeed went to ground.
If possible, I always replace any hard wired mic or a DIN jack for that matter, with a 4 pin Cobra standard connection. This one wasn’t too difficult. It already had a hole in the frame that only needed slight enlarging. I assume that was some engineer’s plan of placing a DIN jack in that spot, but got rejected later. My Dremel slowly removed the metal around the jack to make the covers fit snugly against it. This took about an hour with my limited cutting and grinding wheels. After destroying a couple stone wheels in the process, I moved on to using diamond ones. The covers were painted flat black, plus I usually apply stainless steel screws to all my cover restorations like this one. The original hard wired mic utilized 5 wires, plus both cartridge wires bypassed the key entirely and were connected directly to the radio instead. As you can see, I added a small relay inside the back of the frame to bring the total mic wire count down to 4. The original mic was also rewired with a 4 pin plug to accept this new configuration. All my mics now work great on this radio.
One crystal was off by 2.5Kc’s. That not too bad, but with a little inductance added in series, that crystal is now dead on frequency. I may replace that crystal later, but so far it remains stable. Surprisingly the others are well within a half Kc.
A standard alignment was done according to the service manual that resulted in about 3.5 watts RMS with 80% modulation, a little higher with a power mic. That is sufficient enough for me. It has a single conversion receiver with a low noise RF amp and a 455Kc IF. It has enough sensitivity and selectivity for the normal usage, but I wouldn’t recommend this radio as a weak signal seeker. I never stress any radios, especially my labor of love one of a kind babies.
All parts that I could feel remained cool during a 3 minute key down with a continuous 1K modulated tone. This one should now last longer than my life and make someone a good backup or starter radio for a fair portion of theirs.
Other service done:
Deoxit Fader Lube applied to the Volume and Squelch Pots. Note: I love pots that have an opening to spray into like these.
Channel selector cleaned and sprayed with Deoxit Gold.
Audio output transistors plus driver and final, cleaned and reset with fresh compound.
New power cord with in-line automotive style spade fuse (Purple 3 amp).
The grain-of-wheat bulbs were replaced with LED’s. This feature alone will make the radio run considerably longer on an auxiliary battery.
The face originally had silver paint around the perimeter of the panel and around the channel selector. This trim was so badly worn that instead of trying to repaint it, a pencil eraser worked great at removing it entirely. I may change my mind later, but I’m beginning to like the plain look anyway. Besides, when you’re striping, even the slightest flaw will draw your eyes towards it.
This restoration was time consuming, but at least the SBE Brute has a service manual on CBtricks. As you can see some of the capacitors are packed in tight. The board is not polarity marked so extra care was needed while doing a complete re-cap. The negative side of electrolytic caps usually goes to ground, easy enough, but I noted one cap was reversed in the audio section. It didn’t look correct at first, but after verifying it in the schematic, it did show the positive side indeed went to ground.
If possible, I always replace any hard wired mic or a DIN jack for that matter, with a 4 pin Cobra standard connection. This one wasn’t too difficult. It already had a hole in the frame that only needed slight enlarging. I assume that was some engineer’s plan of placing a DIN jack in that spot, but got rejected later. My Dremel slowly removed the metal around the jack to make the covers fit snugly against it. This took about an hour with my limited cutting and grinding wheels. After destroying a couple stone wheels in the process, I moved on to using diamond ones. The covers were painted flat black, plus I usually apply stainless steel screws to all my cover restorations like this one. The original hard wired mic utilized 5 wires, plus both cartridge wires bypassed the key entirely and were connected directly to the radio instead. As you can see, I added a small relay inside the back of the frame to bring the total mic wire count down to 4. The original mic was also rewired with a 4 pin plug to accept this new configuration. All my mics now work great on this radio.
One crystal was off by 2.5Kc’s. That not too bad, but with a little inductance added in series, that crystal is now dead on frequency. I may replace that crystal later, but so far it remains stable. Surprisingly the others are well within a half Kc.
A standard alignment was done according to the service manual that resulted in about 3.5 watts RMS with 80% modulation, a little higher with a power mic. That is sufficient enough for me. It has a single conversion receiver with a low noise RF amp and a 455Kc IF. It has enough sensitivity and selectivity for the normal usage, but I wouldn’t recommend this radio as a weak signal seeker. I never stress any radios, especially my labor of love one of a kind babies.
All parts that I could feel remained cool during a 3 minute key down with a continuous 1K modulated tone. This one should now last longer than my life and make someone a good backup or starter radio for a fair portion of theirs.
Other service done:
Deoxit Fader Lube applied to the Volume and Squelch Pots. Note: I love pots that have an opening to spray into like these.
Channel selector cleaned and sprayed with Deoxit Gold.
Audio output transistors plus driver and final, cleaned and reset with fresh compound.
New power cord with in-line automotive style spade fuse (Purple 3 amp).
The grain-of-wheat bulbs were replaced with LED’s. This feature alone will make the radio run considerably longer on an auxiliary battery.
The face originally had silver paint around the perimeter of the panel and around the channel selector. This trim was so badly worn that instead of trying to repaint it, a pencil eraser worked great at removing it entirely. I may change my mind later, but I’m beginning to like the plain look anyway. Besides, when you’re striping, even the slightest flaw will draw your eyes towards it.
