with DJK's comments
here's an updated PDF -- I don't think that the MPW3700 is available anymore -- 200VRR in DO41 case -- the MPN3700 is available in TO-92.
I changed cr1, cr8; placed the RC combo from the servo amp in parallel;changed r27 to 1 ohm; flipped the power transistors -- (these are shown as IRF parts although the originals are Hitachi);the VAS transistors are shown as 2sb649,2sd669 - not the originals which are "unobtainium".
DJK -- if it is starting to look correct we should have an administrator cancel the original thread and just use the correct schematic ab initio
here's an updated PDF -- I don't think that the MPW3700 is available anymore -- 200VRR in DO41 case -- the MPN3700 is available in TO-92.
I changed cr1, cr8; placed the RC combo from the servo amp in parallel;changed r27 to 1 ohm; flipped the power transistors -- (these are shown as IRF parts although the originals are Hitachi);the VAS transistors are shown as 2sb649,2sd669 - not the originals which are "unobtainium".
DJK -- if it is starting to look correct we should have an administrator cancel the original thread and just use the correct schematic ab initio
Going to dig this thread up, as I may be fooling with one of these shortly...
If VR1 is controlling bias current, what is VR2 doing?
jackinnj, might you expound on your notation for these pots ('Key=A' and 'Key=Space 50%')?
With the 0.25 ohm source resistors, I assume that matching of the outputs is not as critical as it might otherwise be?
If VR1 is controlling bias current, what is VR2 doing?
jackinnj, might you expound on your notation for these pots ('Key=A' and 'Key=Space 50%')?
With the 0.25 ohm source resistors, I assume that matching of the outputs is not as critical as it might otherwise be?
Hi, I moved to France the Basque Country) a few years back with my Sumo Polaris 310. A month or so ago, one channel went awol. I found a local audio repair store in Bayonne who has got it working but does not know how align VR1 and VR2, so he is afraid it will overheat, he wants to be able to test TP1 and TP2 with a multimeter and needs to know the mv across these 2 (if in fact that is the correct way to deal with the issue)
I should point out that the whole of our conversation was carried out in French which when it comes to electronics I am worse than useless so I may have got something a bit wrong!!?? Hoping you can oblige as I am missing my Sumo big time.
I should point out that the whole of our conversation was carried out in French which when it comes to electronics I am worse than useless so I may have got something a bit wrong!!?? Hoping you can oblige as I am missing my Sumo big time.
Vr2 Adjust on Sumo Polaris 310
I thought I would post the best setting for bias and give every one that's struggling over the Vr2 setting a little heads up. For reference this unit has the original Toshiba Fet's. BIAS=10Mv +/- 1Mv, make sure you do the initial setting after the amp has been on at least 20 minuets. Once you BIAS has been set run the amp at >66Wrms or better but no more than 90Wrms. The reason I say not more than 90Wrms and your measurements for Vr2 will be off. Now run the amp into your load for another 10 minuets and let it rest with no input. Recheck the Bias and reset if needed. You may find one side may have a litter higher bias current then another but as long as you have them within 1mv your fine, one side at 10.3Mv and the other 11.2MV is typical. Now moving on to Vr2. You really need a distortion analyzer to set this correctly but one can get by with just a scope and get close. I have read a few post here and there that setting Vr2 in the middle is OK, well its not. Run the amp at 66Wrms and adjust Vr2 for cleanest waveform or lowest THD . I have attached a shot of before and after. Good luck with all your repairs.
I thought I would post the best setting for bias and give every one that's struggling over the Vr2 setting a little heads up. For reference this unit has the original Toshiba Fet's. BIAS=10Mv +/- 1Mv, make sure you do the initial setting after the amp has been on at least 20 minuets. Once you BIAS has been set run the amp at >66Wrms or better but no more than 90Wrms. The reason I say not more than 90Wrms and your measurements for Vr2 will be off. Now run the amp into your load for another 10 minuets and let it rest with no input. Recheck the Bias and reset if needed. You may find one side may have a litter higher bias current then another but as long as you have them within 1mv your fine, one side at 10.3Mv and the other 11.2MV is typical. Now moving on to Vr2. You really need a distortion analyzer to set this correctly but one can get by with just a scope and get close. I have read a few post here and there that setting Vr2 in the middle is OK, well its not. Run the amp at 66Wrms and adjust Vr2 for cleanest waveform or lowest THD . I have attached a shot of before and after. Good luck with all your repairs.
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Hello, hope you can help. I'm trying to check bias on a 310 and there are no official test points, nor do I have data on the correct setting for each VR. I had posted a new thread last night, but no replies yet, and you appear to be very familiar with this amp. Can you help? Thanks in advance!
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