Loud snap or popping noise when switching on TRC-918

Hi guys 'n gals. Just searching around for a solution to the loud pop noise that my 918 makes when I turn it on.

Tried the following but nothing seems to have any effect so far:
->Replaced filter cap (3300mf @16V with 4700mf @25V) I know wrong mf but voltage was just reduced a hair which shouldn't effect it.
->Cleaned all contacts, switches etc.
->Tried on batteries, & alternative dc input
->checked and fixed sloppy soldering job on power pcb

Does everyone have this same issue? I found one post from superduper stating that its just something we lasonic owners have to deal with cause of poor/cheap design. Is that so?

Really is there anything that can be done here? The sound makes me not want to use it and its such a good sounding box I'd hate to just sell it.

thanks!
=k2j

i think this happens because the amps output caps store a small amount of energy that surges when you turn the power on . there is a delay action taking place between the power being applied and the storage caps being charged to full capacity , this also happens on some of the cheaper old skool car amps , my honest opinion is it's due to the lesser expensive internal parts. i think also it could have something to do with the caps on the power supply board getting old and drying up. my 920 does the same thing.

Damn, then this thing is unusable. I swapped the only electrolytic cap on the power supply board. Didn't do the ceramic ones though, what do you think on those? This stuff is just for Ac-Dc conversion...still happens with batteries and another ext dc source too, so I'm guessing it wont work.


Also would pay for if I can find a set of schematics for this model. Need to figure out which VR is the 19k one on the tuner board so i can sync stereo. Wonder if Albert @ lasonic has any of the old manuals for sale or scan?

Extra circuitry is needed to suppress the turn on pop. Cheap brands such as Lasonic chose to save $$$s and omit this circuitry.

jimmyjimmy19702010 said:

Extra circuitry is needed to suppress the turn on pop. Cheap brands such as Lasonic chose to save $$$s and omit this circuitry.

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:'-( :'-( :'-( :'-( :'-( :'-( :'-( :'-( :'-( :'-( :'-( :'-( :'-(

And for the record My TRC-920 does NOT pop.

So I can only assume there must be some components failing or something for this to happen

dude my 920 pops but my 918 don't so i got the reverse of what you have lol.

Could be that earlier models had the suppression circuitry & later models omitted the feature to save money & compete with other brands....Lasonics will be oK with the turn on 'bump' so don't worry about it, even if it sounds ugly....

Cpl

JVC Floyd said:

dude my 920 pops but my 918 don't so i got the reverse of what you have lol.

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Now that's some funny sh*t

I don't believe Lasonic ever had any schemes. But I've seen some that pop and some that don't. I usually lower volume all the way down to be safe before powering up


Bad Boy Bill

Cpl-Chronic said:

.Lasonics will be oK with the turn on 'bump' so don't worry about it, even if it sounds ugly....

Cpl

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Well, this sound is more like a snap. Like have you ever soldered in a capacitor in backwards and had it pop? more like that sound and almost as startling!

baddboybill said:

I don't believe Lasonic ever had any schemes. But I've seen some that pop and some that don't. I usually lower volume all the way down to be safe before powering up


Bad Boy Bill

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I'll have to try this, but I think I did and it still snapped.

I do this as precaution on all my boxes


Bad Boy Bill

There has to be schematics somewhere for these. they were built with em..

There has to be schematics somewhere for these. they were built with em..


You kidding this is Lasonic we are talking about. They don't even have a scheme for the I931's


Bad Boy Bill

baddboybill said:

You kidding this is Lasonic we are talking about. They don't even have a scheme for the I931's


Bad Boy Bill

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Yeah, that snap that you hear is Lasonic's 'QUALITY' engineering & design...
Cpl

baddboybill said:

You kidding this is Lasonic we are talking about. They don't even have a scheme for the I931's


Bad Boy Bill

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I know man, but someone had to design the boards and send them off for production. Its not like someone hot wired a radio together then sent it to a factory where they just looked at and copied it. There are notes or drawings somewhere.

And I wanna know who shot Kennedy.... somewhere somebody knows something.

I know I asked I asked Albert at Lasonic years ago and he said he don't know if there were ever any so looks like we are all SOL!!!


Bad Boy Bill

None of my 920's pop, but my 918 does

baddboybill said:

I know I asked I asked Albert at Lasonic years ago and he said he don't know if there were ever any so looks like we are all SOL!!!


Bad Boy Bill

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I also spoke to Albert about it and he mentioned something about having boxes and boxes of old documents, but wasn't sure what was what. I volunteered to search through it all with the idea of making it public, but he was so busy, he didn;t show any interest. Maybe one day.

Lasonic TRC-920 said:

None of my 920's pop, but my 918 does


I also spoke to Albert about it and he mentioned something about having boxes and boxes of old documents, but wasn't sure what was what. I volunteered to search through it all with the idea of making it public, but he was so busy, he didn;t show any interest. Maybe one day.

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Fingers crossed Chris. Hopefully someday we'll get lucky. I know, grab Geraldo and you guys can do a documentary!!