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Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Komet's picture

Hello Fellow HiFi Engine Folks,

Does anyone out there have experience in setting the amp bias and dc voltages on Pioneer's SX-D7000 receiver? I downloaded the service manual for it's sister receiver the D5000 and compared the schematic with the main driver board on my D7000 and they look similar but the voltage test point pin out numbers don't seem to be the same.
The instructions and voltage specs for these adjustments seem vary vague and left up to the interpretation on the service tech.
Now since I've never worked on this particular model of receiver before my observations may be out in left field and I'm probably missing something.
Also would like advice on proper voltage/wattage lamps for the bass/treble slider pilot lights. I have new 8V/35ma replacements and measured 8.56 VDC on the leads, so these should be okay all-be-it they may burn a little brighter and not last as long due to the higher than rated voltage? Thinking about adding a small droping resister in series with the hot lead?
Any help or comments would be appreciated.

Thanks,
Komet



Komet's picture

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Tom,
Thanks for all your help everything worked out great adjusting the amp on my SX-D7000. Pots were a little spotty but a shot of DeOxit on each made them usable. She sounds great and still had that warm Pioneer sound I'm so familiar with from their older units (SX-828, SX-1010, SX-990, SX-524). Singing good on my Klipsch KG-4s, this receiver really tames down the horn and tightens up the bass on these speakers. CD's really come thru with an analog edge. Now to replace a back light on one of the input buttons and she'll be good to go. I think this might be a keeper, at least for awhile!
Kris

Komet's picture

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Tom,
Thanks for the update, I will definitely check out the service manual for SX-D7000. Now actually that you mentioned it in regard to the SX-D7000 having different test terminal numbers than the SX-3900 even though their circuits are very similar....this is what I was referring to in an earlier comment. This is what was confusing me....now with the correct test terminal numbers I should be able to make my adjustments quite easily!
Thanks,
Kris

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Kris,

Good luck!!. Just be very careful. When those board have a problem, all 4 outputs fry, along with a whole lot of other transistors resistors, diodes, and even a 20W 3 ohm resistor on the capacitor power supply board. I know, because I had one (sx-3900) go up in smoke on me when I was adjusting.
But it seems like your board is OK, and just needs bias adjustments. I suggest you use a plastic alignment tool, or a small screwdriver that you wrap with electrical tape (except for the very tip, to prevent shorting anything.
Tom

Komet's picture

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Tom,
Sorry about that you are correct on the original response to my question about lamps, that wasn't your suggestion.
But thanks again for all your input, that makes sense about the voltage measurements on the open circuit.
I'm not new to electronics but I've lost a lot of my field expertise in the subject since my job has put me basically behind a desk for years. Vintage audio has given me a chance to get my hands dirty again and I'm just getting started on repairing all the equipment I have collected.
Now as far as LEDs go I may go that route some day but I have a whole stock pile of these little lamps so for now I will use them up.
Regards,
Kris

Komet's picture

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Hello Tom,

Thanks again for your input on the amp adjustments and I will go back and recheck the DC balance without the "Dummy Loads" attached. Also I will do a closer look of the driver board to find the correct test terminals (my old eyes aren't what they used to be).

Now as far as the lamps go I actually checked the voltage by removing one the lamps (bass slider), stripped back the wire insulation and measured on the bare wires. I could measure the voltage on the other lamp because it is still in the circuit but I assume I would get same results since it is burned out and I essentially would be measuring a open circuit same as if the lamp wasn't there! I think I will go with your the 1/4 watt resistor suggestion....in series with the + lead protecting the soldered leads with heat shrink.

Regards,
Kris

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Kris,

My old eyes require 2 types of reading glasses. 1.75X for normal reading, and 2.00 or 2.25 for working on electronics.

While I didn't make the 1/4 resistor suggestion, I don't think you need to do this. Just put the replacement bulbs in the unit.
While I don't have a sx-D7000 schematic, I do have the sx-D5000, which has a good view of the power supply which is probably the same as the D7000.
These units use DC for all lamps. AC from the transformer is rectified, and then fed through a regulator IC producing 8.5VDC "regulated" This will maintain a pretty steady 8.5VDC preventing brightness of bulbs to change when more bulb load is put on. On the circuit boards there are 12 ohm resistors in series with the power bulb, function bulb array, and probably other feature bulbs including the 2 that are bad. When you measured the "open bulb" you measure the full 8.5V because there isn't any continuity. When the good bulb is installed part of the 8.5v will be seen across the 12 ohm resistor, and the larger portion across the bulb. I think you will be fine, although the brightness of the bulb may be a bit different than the original 8V 100ma bulbs
Tom

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

one last idea on the "bulbs"
I have experimented with many types of LED's I purchased on ebay. Many different sizes and styles, as well as various colors. I have converted some of my units to use "All LED" instead of lamps.
You can get small ones with attached pigtails that have the series load resistor for use at 12V, and have seen some at 8v. I would think the standard 12V versions would give more than enough brightness for these functions as they start to illuminate at 6 volts. And you could get creative with Reds, Blues, Greens, or yellow. And LED's will probably last longer than the unit, never needing to replace again.
But remember these are LED's being connected to a DC supply. Polarity needs to be observed as they will work in only 1 direction.
Tom

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Can't comment on the adjustment, but running an 8v bulb at 8.65v will approximately cut the life in half. I assume the 8.65v is measured with the lamp in the circuit. If not, it might drop when the lamp is lit.

Something like a 22 ohm 1/4W series resistor should give you the rated 8v across the lamp from an 8.65v supply.

I guess you could also use a forward biased silicon diode, which will give you something like a 0.6-0.7 volt drop across it at low currents.

Komet's picture

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Tom,
Thank you for the great info on adjusting the power amp other SX-D7000.
Actually per your recommendation I had already downloaded the service manual for the SX-3900 seeing that it is similar to the D7000. But this is were I got confused because the pin numbers on schematics for the 3900 didn't seem to correspond to the pin numbers on actual driver board.
I assume the 56mv and 70mv bias voltages on based on the 0.5ma idle current stated on the schematic?
Now you are right about the pots ....they are spotty, wondering if this could be remedied with a drop of DeOxit?
Also when measuring the DC Balance voltage you do so on the speaker outputs using a DVM in parallel across the 200W Dummy Loads or do you measure at the pins on the output of the relay (21,22,23,&24)?
I will look everything over again and give it another try and comment on my results

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Hello,
The test points for each side, from what I remember are 2 jumper leads across an opening in the circuit board. They are not "pins". The adjustments for DC bias are done without any speaker or load connected.
The easiest way to set the DC balance is, "under no load", connect the volt meter across your speaker terminals. You should not have 200w resistors or speaker load connected while setting DC balance.
I only connect the meter across the load when doing a "Burn in" test, to keep an eye on the DC volts. I don't do any adjustments during burn in.
I am not sure where you are seeing the .5ma idle current on the schematic (sx-3900)?? I do not look at any currents when setting bias or balance. I only look at mv. As close to .000mv on balance, and .065-.070 after the second bias adjustment.

You can try and clean the bias pots using a cleaner first (make sure it is safe on plastic) and then a small shot, or drop of deoxit. But sometimes this doesn't work and you need to replace them, but replacements usually have different pin layouts requiring some creativity. Hopefully you can clean originals. I have found decent substitutes on ebay. If replacing them, use the multi turn type as they are more gradual in their adjustment. What is kind of important is to be able get full range on these bias pots (0 ohms to its value) because these adjustments will affect one another.
Last but not least, be very careful of the bias diodes screwed to the heatsink (if you need to remove the driver from the heat sink). These are special dual diodes and almost impossible to find.
Good luck,
Tom

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Hello,
Look at the service manual for the pioneer SX-3900. This output board and bias setting are more similar to the D7000.
The D5000 is closer to SX-3800 design
Tom

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Also you need to be careful with these settings. They are very sensitive, and misadjustment can cause a whole lot of shorts, opens, and flaming resistors. Also be aware that the adjustment pots get very spotty, and sometimes require replacement.

These are major setting differences between the sx-d5000 (like the SX3800), and the SX-d7000 (like the SX3900) (works best to use 2 meters)
SX-D-7000
Set VR3 for 56mv on one side betweens pin 12 and 11, set VR4 for 56mv on the other side, between pins 9 and 10.
Then you set VR5 for 70mv on the first side between pin 12 and 11, and then set VR6 for 70mv on the other side, between pins 9 and 10.
(If you want your unit to run a bit cooler, set VR3 and VR4 for 51mv, and VR5 and VR6 for 65mv)

If you were setting up an SX-D5000 (like the SX-3800) the bias current settings are higher 120mv first then 150mv second. So don't use the SX-5000 procedure for setting up a sx-D7000 or you will cause overheating and problems.

I have repaired a lot of SX-3800's, SX-3900's, and some sx-D5000's and some SX-D7000's. These are very tricky units that can easily fry many components on the driver board and output transistors. There are also 2 different versions of driver boards that have different protect circuitry (The 115v US only, and worldwide model use slightly different driver and power supply regulator boards, but the driver and output stages are basically the same)

I built a test jig for working these units specifically, to look to find problems that can cause catastrophic failure before the board is damaged. I connect a 60w incandescent light bulb in series with the hot leg. I then turn VR3, VR4, VR5, VR6 fully CCW, and VR1, VR2 to center position.
I then power on the unit
The 60W bulb should come on bright and slowly dim to almost nothing. Its purpose is to limit the total current to about .5A going to the receiver. This keeps from burning anything.
As the 60W dims, the receivers lamps should begin to light up, and the protect relay should energize
The unit should actually be working and producing sound
I perform rough bias adjustments to make sure that they can be made, and that the pots aren't spotty.
Note that as you increase bias voltage, the 60W will start to brighten a bit, and you may even have the protect relay drop out. Don't worry as you are really just looking to see if pots are bad.
If the pots are good (not open or spotty), and you are able to get the 56mv and 70mv adjustments done on both channels, you can shut and unplug the unit.
Now turn VR3, VR4, VR5, VR6 fully CCW, and VR1, VR2 to center position.
Plug in and power on the unit
Wait 10 minutes
Perform the bias and DC balance adjustments as in the SX-3900 service manual.
Make sure they don't drift too much, but they will drift as the temp of the outputs/heat sink change.
Power off and remove the test leads

I then use 200W load resistors and crank the unit for a while with volume control at the 12 noon position. I attach the test leads from both meters in parallel with the load resistors to look at the DC levels.

I then shut down, remove the loads, and let the unit cool for 30 minutes.
As a final check i connect the meters back to the bias test points, turn the unit on, and verify that the DC bias level is ~70mv in 10 minutes.

Pionner SX-D7000 Bias & DC offset Voltage adjustments and specs

Kris,

I just noticed that someone has posted a copy of the SX-D-7000 Service manual. Looking at it, the only differences are the identification of the bias test points.
I described which test points to use based on the SX-3900. The SX-D7000 refers to them as "JP". They are actually jumper wires on the board identical to what is on the SX-3900 except called JP13, JP15 (instead of no 12, no 11), and JP23, JP25 (Instead of no 10, no 9)

JP13-JP15 set the left channel bias, and JP23-JP25 set the right channel bias

Or just follow the newly posted SX-D7000 amplifier adjustments.

Tom