Bob Carver Corp RAM285 bias not working correctly

[Nahash5150 10,955]

For those experiencing issues with the bias setting on the RAM285, the issue is likely with the burn-in effect of the circuit and transformer winding that powers the bias circuit. Many Bob Carver Corp amplifiers experience this trouble. Common complaints are:

 

- The bias does not adjust high enough.

- The bias does not adjust low enough.

- The meter is not working.

 

Unfortunately, there is no DIY fix for this. The RAM285 has extremely unfriendly serviceability. The PCB hides most components and is multilayered. Reworking the circuit board requires technical experience and proper tools. Moreover, the trouble has common causes but it may also be related to other less common troubles, so the amplifier should be fully tested to verify what the real trouble is.

 

Please inquire with us to get your RAM285 serviced if it is experiencing any trouble. 

 

[Rob 6,267]

Greg, I haven’t had this problem yet. Is there maybe a certain amount of hours before it appears? Or is a bad transformer? 

[Kurt 3,167]

I haven't touched the bias adjustment on mine.  I was advised I may never need to do so.  

 

How would I know if I have an issue?

[Kurt 3,167]

8 hours ago, Nahash5150 said:

 

 

Please inquire with us to get your RAM285 serviced if it is experiencing any trouble. 

 

Related question...... is Nelion taking over the warranty work from Jim Clark?... I know he closed up his shop, got a new job and has been real busy. 

But, on his way out, he did say the warranty's would be honored.

[Nahash5150 10,955]

15 hours ago, Kurt said:

I haven't touched the bias adjustment on mine.  I was advised I may never need to do so.  

 

How would I know if I have an issue?

 

 

The bias should stay between 50mA and 150mA at idle after 10 minutes of warm up. If you've chosen your sweet spot, say 90mA (because that's mine), then it shouldn't change. If it does by more than a few mA, then it could indicate a problem, especially if it won't adjust properly or keeps falling out of your sweet spot.

 

15 hours ago, Kurt said:

Related question...... is Nelion taking over the warranty work from Jim Clark?... I know he closed up his shop, got a new job and has been real busy. 

But, on his way out, he did say the warranty's would be honored.

 

We aren't taking over the warranty. We are just willing to service these units and do our best to support them, unofficially, because right now, there is no official support.

 

21 hours ago, Rob said:

Greg, I haven’t had this problem yet. Is there maybe a certain amount of hours before it appears? Or is a bad transformer? 

 

I'm sorry I don't know the exact origin of the trouble. I just know that it seems to be related to time, nothing else.

[Kurt 3,167]

Thanks @Nahash5150. That's helpful.  I've logged a lot of hours on my 285....haven't noticed any issues.  I'll check the current bias reading and let y'all know.

[Kurt 3,167]

Just a data point for you... 

 

I checked my bias meter.   It's steady at 75mA at idle and seems to move just fine while playing.

 

I have had my 285 since May of last year.  I'm probably putting 4-5 hours per week on it, I'd say.  So, close to 300 total hours, i'd say (also this is the unit that Steve Guttenberg used for his review, so, it had some hours on it before I got it).

[jjptkd 1,516]

On 7/20/2025 at 6:36 AM, Nahash5150 said:

The bias should stay between 50mA and 150mA at idle after 10 minutes of warm up. If you've chosen your sweet spot, say 90mA (because that's mine), then it shouldn't change.

 

We aren't taking over the warranty. We are just willing to service these units and do our best to support them, unofficially, because right now, there is no official support.

 

 I wanted to say thank you for taking the time to look at and fix my amplifier- I've had it back in the system for a few days now and it appears to be working perfectly again. As much as I enjoy the 275 amplifier the 285 is head and shoulders better IMO; it has the warmth and tubyness while at the same time solid state like bass and clarity and good high end which by comparison seems pretty rolled off on the 275. Anyway, thank you for stepping up and offering service for this great amp- while frustrating that @Ar9Jim Jim Clark ducked out it is understandable and I don't harbor any hard feelings towards the guy. 

 

Jesse

[jjptkd 1,516]

On 7/20/2025 at 2:47 PM, Kurt said:

I checked my bias meter.   It's steady at 75mA at idle and seems to move just fine while playing.

 

I have had my 285 since May of last year.  I'm probably putting 4-5 hours per week on it, I'd say.  So, close to 300 total hours, i'd say (also this is the unit that Steve Guttenberg used for his review, so, it had some hours on it before I got it).

 

That's about roughly when I started having trouble with mine, around 300 hours or so. It started with a loud "PoP" shortly after power up, I was in the other room and heard it quite loudly through the speaker(s.) Amp still sounding fine so shrugged it off. A couple days later noticed the meter was only reading 20ma or so and when I tried to re-adjust the bias it would max out at around 55ma? 

 

It's a little funny, I've seen you mention before that you had the "review" amplifier- I wonder which one of us actually got that amp as I supposedly bought that amp too. I don't really care if I'm being honest I just jumped after it because of the $500 discount that was offered at the time, which he ended up extending to all new amp sales anyway. 

 

 

Jesse

 

 

Edited August 4, 2025 by jjptkd

[Kurt 3,167]

5 hours ago, jjptkd said:

It's a little funny, I've seen you mention before that you had the "review" amplifier- I wonder which one of us actually got that amp as I supposedly bought that amp too. I don't really care if I'm being honest I just jumped after it because of the $500 discount that was offered at the time, which he ended up extending to all new amp sales anyway. 

 

Wow, that is so weird.  I responded to the same thread when Jim offered the discount on the Guttenberg unit. Though, when I look back at my emails with Jim, while I did ask for the Guttenburg unit, he never came right out and said that's the one he was sending me.  So it's entirely possible I got something else.  I assumed the one I received was the review unit, though.  Because, 1) I got the $500 discount and 2) when the Amp arrived, the tubes were already installed and a screw on the back plate was not tightened all the way, as if someone had opened it up, looked inside and didn't tighten all the screws back up.  So, it seemed "used" to me.  Also the box it came in had been taped closed, reopened and retaped.

 

I guess it doesn't matter.  The main reason I mentioned that I had the review unit was just to make sure folks had all the info when making diagnosis/comparisons and offer up one reason why my unit may have some differences.  

 

Now you have me even more worried that I have a ticking time bomb in my bias meter!

 

 

Edited August 4, 2025 by Kurt