I was informed by the company that sold me the FM transmitter that the pre-emphasis defaults at 50 µs and that is how my transmitter is configured at 50 µs. I am in the USA and the pre-emphasis is not set by simple programming, instead, it is done by a resistor/capacitor configuration on the main board
I am including two photographs, one is an image that was sent to me on how the pre-emphasis is set and the other is an actual image showing the BH1414K chip and the associated resistor/capacitors on the PC board.
The seller says two capacitors have to be changed which is C3 and C4 to set the pre-emphasis to 75 µs. A few have told me there has to be more to it than that such as changing out both a capacitors and resistors at the same time. I wish to know if this is true, that both a resistor and capacitor have to be changed or if the seller is correct about only needing to change C3 and C4 to a 1500pF capacitor.
First off does anyone know anything about the BH1414K IC chip? Second, I am not able to get an actual schematic diagram as I was told that can not be given out to the public.
Please check the photos and give me as much help as you can.
Photo below was sent to me by transmitter seller who said C3 and C4 should be replaced with a 1500pF capacitor.
(click image below to blow up and scroll) Left side is full board view, right insert is zoomed in view of chip area with part numbers.
[image removed - violated original posters source]
Below is the actual chip in question on the main circuit board of my transmitter. Below the BH1414K chip are the capacitors that were mentioned in the map above.
(Click image below to blow up to larger size)
[image removed - violated original posters source]
This chip above, is normally hidden under a large shielding plate.
suzy.... I have the EXACT same transmitter!! And the mod advice you got is EXACTLY what I got from my vendor..... The capacitor swap out SHOULD do the trick...be SURE the replacement caps are conservatively rated - ie., 50WVDC - to avoid over-voltage issues... After several attempts at installing these "micro" caps....I finally gave up on the project!! You'll need a GOOD magnifying lens/lamp, a HIGH-QUALITY temperature-controlled soldering iron with a micro tip.....and hands that are surgeon-steady!! It doesn't take much to create a solder "bridge" on the circuit board....or overheating an adjacent component! IF your transmitter is NEW....or still under warranty....I'd STRONGLY consider returning it (Yeah, i know shipping to China will be pricey....!) and getting a transmitter already set for 75uS preemphasis....I ended up scoring a CCA 20 watt exciter and power amp on eBay...running with an Optimod 8000A it sounds like a DREAM!! I have a 25 watt unit for sale.....PM me if you're interested.....
This thread is an exact duplicate of my thread, the words and pictures are identical with the exception of the same suzy, please check this thread and you'll see what I mean.
In fact, even the topic title is the exact same as mine. Only two differences between both threads, is the links to the BH1414K IC chip PDF are different and the name suzy Vs. Bruce.
I don't even understand why someone would do this, it's not even spam, just weird parroting. Anyways thread locked until I figure out what the hell is going on. We have had spam before but this doesn't even make sense. Time to cull the herd of randoms I suppose. MrEd feel free to PM me if any further issues pop up. Being an open forum we occasionally get strange things that happen like this. Locked and thrown into the bin for now.