RT1000P sub amp circuit board question DESPERATE!

womo · February 18

For my old RT1000P, both subs are blown. I can replace a leaking capacitor, but both have one particular resistor (R33) that is burnt up so bad I cannot make out the color bands, so I don't know the value to replace them with. Anyone have the board available and can tell me the color bands on R33 (gold band last) I would be eternally grateful. And I may actually be able to get my subs back online. Thanks!!! Keith

womo · February 18

I've read the RT1000i uses roughly the same board so it might have the same R33 resistor. Worth trying if I can't find anything out about the P board. Thanks

F1nut · February 18

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/132074196092

WLDock · February 18

Check out my March 2015 reply: https://forum.polkaudio.com/discussion/comment/2118495/#Comment_2118495

It looks to be a 220 Ohm. or whatever they mean by: 220/0.SW

womo · February 18

OMG Thanks so much! You saved the day. Yes, schematics say 220, .5W. Maybe they should have put more heat tolerant resistors in, both speakers they're burnt toast. One cap is oozing, but the others look fine. I may replace them anyway while I've got the tools out. They can't be that expensive. Hopefully find them at Fry's here in Atlanta, or Polk directly maybe? I'm encouraged now that it may just be those resistors and cap. Thanks again!

womo · February 18

You think that shape resistor is a special type that I should look for specifically, maybe heat tolerant...?

FestYboy · February 18

Shape and size isn't special, it's that way due to the wattage rating. Not sure it's a heat issue, more like it's alway at the wattage limit and something further down the circuit pulled just a little more than usual and "poof". Throw a 1w resistor at it and never have that problem again.

womo · February 19

Well no luck with the first speaker. Replaced the resistor with a new 220, .5W. The caps on this speaker's board look fine (possible they're not I suppose). I did buy four 4700uF 35V (no 25V available, hope that's OK...?)

So with just the resistor replacement, this speaker powers up ok, with no signs of overheating, etc. but so far no bass output at all, hi-level with jumpers on, or off line-level, auto and OFF, varying the speaker's volume pot, etc...

I'm a bit confused by the resistor schematic value of 220. The old one is burnt pretty bad, but the first band is pretty clearly brown, not red. I guess possibly replaced improperly by a previous owner, but I don't think so... it looked pristine on the board. Maybe the schematic is in error?

After letting the speaker run a while (board is powering up) I don't see any signs of overheating so far. Guess my next step would be to replace the two 4700 caps on this board, or maybe the power transistor... But not sure at this point if its really worth hit and miss of every suspicious component on the board. Any thoughts or suggestions how to proceed?

WLDock · February 19

womo wrote: »

I'm a bit confused by the resistor schematic value of 220. The old one is burnt pretty bad, but the first band is pretty clearly brown, not red. I guess possibly replaced improperly by a previous owner, but I don't think so... it looked pristine on the board. Maybe the schematic is in error?

The resistor looks to be a basic 220 Ohm .5W carbon film resistor

Remember that part of the circuit is the hi-level/speaker level input and the resistor is in parallel with the output from your amp/receiver and tied to ground. . So the resistor does see some heat. I would think a metal film or metal oxide type would be used here but maybe not. As far as troubleshooting, it could be a number of things so its hard to say. Much depends on your skill level and how far you want to dive in.

womo · February 19

Yep, that's what the ones I bought look like. Strange that the ones on both L and R boards have a first band brown (see my pic above). I have to think the prior owner must have replaced them at some incorrectly.

womo · February 21

I'm really just looking to get some of the mid-lows from the 6.5" mid-woofers. I have a separate powered sub that I can turn on for some low bass, although frankly I rarely turn it since its just too much for my small living room even at low volume, and the neighbor will bang on the wall (true lol). Is there anyway to just make the RT1000P 3-way, wiring the 6.5" into the speaker's crossover (or installing another crossover maybe). Just seems like my Denon amp would have more than enough power to handle all three drivers, including the 6.5", directly...

womo · February 21

Or maybe i could just install some small basic amp boards in the box to replace what's there and use the speaker's existing crossover sub line level as input for it, to drive the 6.5s. I do really like the sound of these speakers, but wouldn't mind hearing a little more mid lows that i suspect those mid-subs in there can deliver.

EndersShadow · February 21

Power it with a iNuke 1000DSP or similar.

It’s got onboard EQ so you can play with it however you want.

Lots of folks have done some similar for MF-15 subs that have bad plate amps (common issue and company went under)

womo · February 22

I'm not sure i understand how this speaker works. If i have it wired up with the jumpers on, no subwoofer line level in, and the switch set to off, does that mean it should be acting as a 3-way passive crossover to all three drivers? Because when I have them hooked up this way tweeters and mids are fine but i get NO output from the woofers. So does this mean the problem is with the crossover boards, not providing low pass? If so where are those boards and how do I even get to them?

womo · February 22

OK from the schematic it appears that the crossover only feeds the tweeter and mid-sub. The sub-woofer comes directly from the plate amp, where the low-pass filtering is happening too I assume. If I'm not mistaken both mid and sub woofers are the same 6.5" 7011 drivers -- the sub just gets some added bass from the enclosure. From Polk: "High Velocity Compression Drive bandpass enclosure joins with Polk's Power Port™ system to deliver spectacular bass response". So I guess I'm SOL as far as wiring the subs in unless I can get the plate amps working again.

RT1000P sub amp circuit board question DESPERATE!

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RT1000P sub amp circuit board question DESPERATE!

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