Norm1968 said:
Hi Superduper
You seem to have a great experience. And you are right, I do not know much about modifying such a Box.
You’re not in favor of a converter because of the voltage not being constant. There must be better quality converter?
I have a spare Panny Rx-C100 for parts with the ajustable power-in. Could I use some parts to modify the RX-7200?
When I say ‘’ I ‘’ I am saying a ‘’ technician ‘’.
I found out reading about this great box that, since the RX-7200 is a Japanese domestic model and was never released worldwide the FM band is limited to the Japanese frequency range of 76-90MHz but also that it can be changed. Have you done that?
Thanks Superduper!
Thanks everybody for your input on this subject. It is realy helping and inlighting.
Just so you know, I am pretty green in the field of electronics. I love the boxes but I need a tech to do any type of work on them.
1) you misunderstood, I didn't say I'm not in favor of a converter. I'm saying that a converter, which is like an adapter, is fine because it converts the voltage to the proper level that the boombox was designed for.
2) The RX-C100 transformer could probably be used to "retrofit" the RX-7200, if it was the same physical size. It might be bigger. When I did this to my 7200, a USA spec transformer of that exact same size was not difficult to find, I would even say a common size. This is the best way to convert the 7200 to USA use, in my opinion. Here's why: A: even if you plan to use a converter, the cord receptacle can still accept a normal USA connector and someone else not familiar with it could inadvertently plug it in without a converter. Or, time could pass and you could forget. B: An adapter is a cumbersome solution. C: A properly retrofitted unit could be used worry free. Just use it like any other USA electronic device.
3) Make no mistake, converting the tuner to USA bandwidth is no small DIY job. I have an article on one of my websites (wikiboombox.com) that describes in detail one way to perform the conversion. However, if you don't mind the cost, you can have member Toshik (here) do it for you. With the high cost of shipping back/forth, it might run you ~$200 to do that though, not sure you will find it worth it. An external tuner can always be used or a bandwidth converter could be used as well (all over Ebay). What that converter does (after install between tuner and antenna) is convert the incoming signal to a different frequency. In other words, if you get one with a 20mhz shift, although the tuner shows 76.1mhz, it is actually receiving 96.1mhz. These are sold primarily to allow Japanese cars or car-radios to work in other worldwide locations.
4) Nothing wrong with being green, everybody was green at one time, and most still are. This is not a box to learn on though. It's complicated enough on it's own being a top of the line product, but because it is a Japanese domestic product, NO service documentation exists for this model that we've seen, so it would be like navigating partially blind, even for a technician, many of whom will not work on it for complicated repairs without documentation.
caution said:
I know the norm is to send the secondary side through a rectifier and filter and be done with it, but have you ever seen a box with a regulator, maybe allow it to get away with a slight overvoltage?
Every boombox has some regulators in it. A few have the regulators right on the PS board but most will have the regulators on the circuit boards somewhere. Typically speaking, only the power amp and some tape motors and solenoids, etc, get unregulated rail voltage. Other circuits are usually powered through regulated rails, and the tuner for certain will receive regulated voltage. For the amp, you usually want as much voltage as possible for maximum output (within module design limits, of course) which is why the secondary voltage is unregulated to the amps. However, keep in mind that each unit sold is marketed to distinct locales, so a unit sold in Japan (100v), USA (120v) and Europe (220/240v) will, unless multi voltage capable, be different versions. Based on the expected maximum voltage the unit will see, the regulators are designed to handle a certain amount of load within a safety margin. I wish I could say that it will be a huge margin but not usually. Capacitors have normal ranges (6.3v, 10v, 16v, 25v) etc. Typically, the next step up will be used. For a 5v circuit, a 6.3v cap will be used. On the RX-7200, the big 6800uf cap by the power amp is a 25v unit. On 120v power, I think I measured around 23.8v. That is without factoring in an fluctuations in the service. I have seen voltage as high as 125V depending upon time of day. Would you run a system like that and expect any kind of longevity? Also, we already discussed previously about regulators. The higher the voltage they need to drop, the higher the amount of heat generated. On many boombox regulators, the driver transistor doesn't even have a heatsink and the zener diode will be passing a lot of current. I've fixed countless transistor/zener-diode regulators that have failed on just normal voltage circuits. It's fair to say that failure frequency will be related to voltage increases. In short, 20 - 25% is not a
slight overvoltage, and could potentially, maybe even likely, rise above design safety margins.
