MN3102/3207 Questions

[electricstorm]

I am working on the Lovetone Flanger and had a question about the biasing of the BBD. There is a trimmer (22K) used to bias the MN3207 at the input (pin 3). When biasing this, what am I looking/listening for? If you need to see the schematic, just click on the link in my signature and click on Daughter Board Schematic. Also, the Morley Sapphire Flanger Box has a similar Bias adjust. I can't find any info on setting this adjustment.

Also, according to the MN3102 datasheet, using a 100pf cap and a resistance of 5k ~ 1m for the R/C network will produce a cp (clock pulse) of 3.2kHz ~ 260kHz. Now, the daughter board has a 120k resistor with an LDR in parallel. After doing some calculations, an LDR of 5k in "full light" in parallel with the 120k resistor gives 4.8k. Is this close enough or should I not go below the 5k limit from the datasheet? If this is good enough, my next question is:

While waiting for my LDR's to arrive (an assortment) could I use a 500k to 1m pot to simulate the LDR as long as I don't go below the 5k or 4.8k limit to see how the circuit responds?

Slightly confused at the moment with these BBD's and LDR's.

Any help is appreciated.

Jim

[Scruffie]

When biased correctly with that trimmer, you'll hear flange, you can tweak it for the least amount of distortion but it'll have a short range where it works.

I'm not sure how you intend to use the pot, you can use one to alter delay but I wouldn't bother, at short ranges unless you lift the dry it'll be hard to hear.

Wait untill it's built then just tweak the trim untill you hear undistorted flange.

[electricstorm]

The idea of using the pot was to simulate an LDR and try to verify the delay. I don't have my order of LDR's in yet (one of the orders is from Futurelec). I had already ordered several LDR's (different values) to try from different sources when the idea of using a pot in it's place occured to me.

Does this make sense?

Jim

[LaceSensor]

Hi

Couldn't f d other thread. I'll get bk to you on the tant and bc transistors as soon as I can
I'm in Norway on business til next week.

[electricstorm]

Thanks Ian!

I've made some progress on the Flanger. The LFO is working. Hope to get the daughter board and rest of the main board going soon. It's slow going for sure.

Jim

[LaceSensor]

Govt lucky sent me your list of needs, I'll address what I can when I'm home

[electricstorm]

Yeah, the two of us have been putting our heads together to try to figure out some of the details on the board.

I ordered a 10uf tantulum cap for C6, but not sure that is the correct value. I know there was a lot of questions, answer what you can and I really appreciate the help! Have a safe trip.

jim

[electricstorm]

Still waiting on the LDR's to arrive, but wanted to get clarification on the BIAS adjustment.

If I am using an audio probe while adjusting the bias, I assume I would be probing the outputs of the MN3207 (pins 7 & while making the adjustment and try to adjust it for the least amount of distortion while getting a delay or flanging effect (I really need to invest in an oscope!). Is this correct?

Jim

[Scruffie]

Still waiting on the LDR's to arrive, but wanted to get clarification on the BIAS adjustment.

If I am using an audio probe while adjusting the bias, I assume I would be probing the outputs of the MN3207 (pins 7 & while making the adjustment and try to adjust it for the least amount of distortion while getting a delay or flanging effect (I really need to invest in an oscope!). Is this correct?

Jim

Really you need a scope as you say rather than an audio probe, I don't think a probe is gunna help much and you'd wanna really test whatever follows the pins on the probe anyway as they're opposing outputs.

Just turn it untill you get flange, then adjust untill you hear the least distortion, easiest way to do it without proper test equipment, you'll get close enough and you can tweak untill the trimmer wears out.

[electricstorm]

Thanks Scruffie! Yeah, I really need to sell some stuff and get a decent oscope. Been looking at fleabay, but nothing I can afford yet.

Thanks again,

Jim