Repair AKA RG 28s mixer - Page 1
Forum section: electronics / repair

author: a__m
author_rank: Newbie
timestamp: February 16, 2022, 10:28:53 pm
content: Hello everyone,I'm trying to rescue an old mixer that was dropped into the water and blown the filter/capacitor. This is a follow-up post, you can find theoriginal post here. Unfortunately, I didn't got any answers there...I got a replacement filter, but the specs are not exactly the same:the amperage, the original is 10 amps the replacement is 6.3 amps.the capacitor differs from 2500 to 2700 pF.Original:Replacement:My questions are:Is it safe to use this as a replacement?Should I add that resistor between lines?I know very little about this, so please be patientThank you

author: a__m
author_rank: Newbie
timestamp: February 18, 2022, 09:13:49 am
content: Am I missing details on the original post? I'm not sure why I'm not getting any answers... please let me know if there is any piece of information missing, I can provide picture of the actual mixer and measure any values from the device.

author: sean0118
author_rank: Frequent Contributor
timestamp: February 18, 2022, 10:43:07 am
content: Post some photos of the mixer, if the filter is fried there's a good chance the motor is too.

author: a__m
author_rank: Newbie
timestamp: February 18, 2022, 11:15:46 am
content: Thank you sean0118 for the reply.Regarding the motor I think it's fine, I did connect directly, bypassing the filter and it spins. Is there any additional test I could do? Here are some images of the mixer, I can get any additional detail if needed, just let me know.

author: a__m
author_rank: Newbie
timestamp: February 18, 2022, 12:40:34 pm
content: I did some testing on the commutator bars of the motor, when reading through adjacent bars I have values between 6.2 and 7 Ω, but then there is a single point where I get a huge spike, that reads 89Ω. Other than that I could not find any shorts from the commutator bars to the armature stack.

author: Alex_Baker
author_rank: Frequent Contributor
timestamp: February 19, 2022, 04:14:04 am
content: That seems like a open winding in the rotor.Do you have a DC power supply? you could try attaching the motor to low voltage DC(barely spinning) to see if there is a spot in its rotation where the torque drops significantly.

author: sean0118
author_rank: Frequent Contributor
timestamp: February 19, 2022, 09:14:57 am
content: Quote from: a__m on February 16, 2022, 10:28:53 pmThis won't matter if the motor is damaged.But to answer your questions about the filter, whether the 6.3A rating is okay depends on what the maximum current draw is, probably has a power rating in watts?The resistor is a bleed resistor to discharge the capacitors in the filter, otherwise the pins on the power plug might remain live once it's unplugged. Some filters have them built in, but if yours doesn't you should add one somewhere. It's across live to neutral so needs to be rated for mains voltage. The original one was probably around 1M ohm?edit: Forgot to ask, the photo that a__m linked in the reddit page shows there's no earth connection. Are the mixer blades normally isolated on these things? Or is it potentially a death trap?

author: a__m
author_rank: Newbie
timestamp: March 08, 2022, 12:33:41 am
content: I'm sorry for the late reply, had to pause on this for a while.Quote from: Alex_Baker on February 19, 2022, 04:14:04 amI did this and it worked relatively smooth, the minimum voltage I could make it spin was 21v and the current oscillated between 0.36 and 0.38. I could feel some difference in the torque but looked more related to the cog wheels in the blades rather than the motor itself.Quote from: sean0118 on February 19, 2022, 09:14:57 amI couldn't find any, it's a quite minimalistic electronic deviceQuote from: sean0118 on February 19, 2022, 09:14:57 amThank you for the detailed explanation. Had no idea that a resistor could be used for this as well.Quote from: sean0118 on February 19, 2022, 09:14:57 amMeasured 1.9MQuote from: sean0118 on February 19, 2022, 09:14:57 amThat's accurate, there is no earth connection. I did some testing on the blades and the other components and as far as I can tell it looks to be isolated.Not sure how should I proceed. What comes to mind is to connect the machine without the filter and measure the current to see if the filter would work. Does this make any sense? Any other recommendations?Thank you.