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Re: Potentiometer and output transistors
Try sony for the transistors, they use them too, but expect a handling and delivery charge from all suppliers these days. It sounds like a standard 330 ohm preset pot by your descriptions. There are more than a dozen varients to chose from. You will need to compare the lead setup and pitch to get the correct replacement. I use Farnell electronics to mix and match odd replacements. Good luck
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You may have a bad speed pot. The speed potentiometer is wired in series with the throttle potentiometer. Try testing the speed pot by testing the resistance or simply shorting across it to test. I usually replace both parts for a complete failsafe repair. Hope this helps.
The potentiometer can be checked with a multimeter ohms range. Analogue is best.
I would be surprised if the potentiometer is faulty but you might be lucky. MIG welders rarely use a pot to control the voltage - most often the voltage or power is adjusted in steps by one or more switches and it is the wire speed and current that uses a potentiometer.
Why would you cut d11 when you can adjust VR4 and have it sound so much better? When you cut d11 you put that modulation into overdrive. Put that diode back and adjust VR4 for 100% modulation. That is step one.
I assume you added variable power from J36. The problem with adding variable power and not switching the pot is that the wires not only have major loss, running to the pot. And two the stock potentiometer tend to burn up if not replaced with a potentiometer that adjust power by itself. Undo this so called "super mod."
Start with a 1969 final for better handling of power.
Adjust VR4 for 100% modulation.
You can pull the ferrite out of the pot next to the final transistor or you can remove j36 and add a 330uf capacitor (black stripe, negative) to the rear and bias the soldier side with a 33uf resistor. Soldier the resistor to the same soldier points of the Capacitor.
The problem is that the potentiometer that the knob is connected to is dirty. This is a common problem with age, or quality of installed potentiometer. (potentiometer is the name of the component that the knob attaches to. It usually looks like a 1/2" long cylinder)
There are multiple solutions to this problem. The first is free & anyone can do. While the unit is off. Twist the knob back and forth quickly and rapidly numerous times. Roughly 10-15 times will do. This sometimes allows for the connections within the potentiometer to reconnect, and remove the crackle.
The second solution involves some handy work. The unit's case will have to be disassembled, and the potentiometer that the knob is attached to must be found. There is usually a relief hole somewhere on the housing. Within this relief hole one can spray contact cleaner. This cleans the contact within the potentiometer which is the cause of the crackle. Once the pot has been sprayed, rotate the knob like in step 1.
If steps 1 & 2 do not work, the potentiometer will need to be replaced. This work usually needs a professional. If you are handy with a soldering iron, it can be accomplished. Look for any particular part #'s on the crackly potentiometer, and then copy these into a online parts catalog. Mouser.com and Digikey.com are excellent resources for finding parts. Upon finding a replacement, it can be swapped out, and provide the user with a crackle free knob.
As always, make sure power to the unit is disconnected. If you are unsure of electronics, please use caution, as dangerous voltages may reside that can cause personal injury.
This is a very typical error code when the throttle potentiometer is out of neutral at start up. This is caused by wear or hitting or bending the throttle lever.
In my experience the best way to adjust the throttle pot is to clean it. I usually replace both the throttle potentiometer and speed potentiometer when they fail, cause an error beep, or they have dead spots. You can carefully remove these components by removing the covers and following the service procedures in the service manual. Very carefully take them apart to clean the wiper on the potentiometer with electronic spray contact cleaner (this is not in the service manual; use extreme care and do it delicately).
You can adjust the spring tension on the throttle potentiometer with careful bending. You can first try to zero out the throttle pot by hand (even it out) and start the scooter to clear the error code. With your left hand adjust the lever left or right and with your right hand turn the scooter on. By trial and error you may be able to get this to work. In both circumstances you will wind up replacing both components anyway and the fixes I have described are only temporary. Hope this helps.
Yes, active use different value pots than passive. The volume control is LIKELY an "audio taper" which can be either an "A" or a "B" marking as there is confusion about the marking. The resistance is likely around 500K ohms down to as low as 50K ohms. The marking MIGHT be something like 504 B or 503 B or the same with the letter "A".
An A500 pot might be only 50 ohms... That would result in very low output. Again, the marking in the industry is not consistent.
Best bet is to get the part from Yamaha. Go to Yamaha America "parts" dept in California. You can search the phone number with Google.
I would replace the output transistors of the bad channel and any very low ohm resistors associated with them. Whilst youre in there replace the electrolytic caps in the power amp section. Caps are cheap and plentiful. I dont know what the rest of the circuit looks like but there might be a need to balance the DC offset after replacing transistors.
matelectronics.com and audiolabga.com carry many good replacement transistors.
usually trim adjustments are on the controller... not on the vehicle itself.
a potentiometer os a fancy word for dial adjustment. It wont be a metal screw, but probably a metal square with a plastic looking slot that can be turned. usually white or blue plastic