A lot of work and diagnosis to get to this point. That was the hard part. Why send it out now? Wouldn't that have been the thing to do in the beginning?
Need someone to fix my Dynasty HT-959 BBX soon.Video inside!
- Thread starter blu_fuz
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No, no, no - he is not troubleshooting the bbx he just has more experience working with vintage electronics so he knows how careful to be with the circuitry. I have about 10 minutes of soldering under my belt and he probably has hundreds/thousands of hours. I told him to just put the new parts in for me, that's it. I didn't give up on the box yet. 
I got it back today.......
AND IT WORKS!
Things that work:
Both channels/speakers produce sound and clearly.
Radio can be heard perfectly clear in FM/AM/SW.
Motors turn for the tape decks but the belts are so stretched I just stopped them.
All lights/LEDs work.
Aux in works great.
Things that aren't quite right yet:
When you get to about 40% volume the speakers will pop once and punch out towards you pretty violently.
The power button still does not turn the box on or off so when you plug it in it is on all the time.
The transformer still buzz's but I was told it is just the metal casing on it and I could fix that easily.
If I even touch the sensor button it will turn the box off. I can wiggle it into a position that will keep the power on though.
I havn't tried batteries yet.
So, all in all I am very happy that it is to this point. Any input is appreciated. Thanks
AND IT WORKS!
Things that work:
Both channels/speakers produce sound and clearly.
Radio can be heard perfectly clear in FM/AM/SW.
Motors turn for the tape decks but the belts are so stretched I just stopped them.
All lights/LEDs work.
Aux in works great.
Things that aren't quite right yet:
When you get to about 40% volume the speakers will pop once and punch out towards you pretty violently.
The power button still does not turn the box on or off so when you plug it in it is on all the time.
The transformer still buzz's but I was told it is just the metal casing on it and I could fix that easily.
If I even touch the sensor button it will turn the box off. I can wiggle it into a position that will keep the power on though.
I havn't tried batteries yet.
So, all in all I am very happy that it is to this point. Any input is appreciated
. Thanks
MasterBlaster84
Boomus Fidelis
blu_fuz said:
Cool blu_fuz glad it's working well now.
You may want to contact Thafuzz about the speaker pop issue, I seem to remember he had the same or similar issue but I'm not sure if he ever fixed.
ViennaSound
Boomus Fidelis
Yeah, perfect!
Wish you the best to get it to a total finish.
But the biggest part seems to be done.
Hope i find some time to work at my AUDIOTON....
Wish you the best to get it to a total finish.
But the biggest part seems to be done.
Hope i find some time to work at my AUDIOTON....
Thanks guys. I was reading up on the speaker pop issue on S2g and everone says "speaker is blown". I know for a fact mine are not blown because I was using the speakers directly with another stereo.
It seems to be popping most when I move around the 100HZ EQ slider :annoyed: .
It seems to be popping most when I move around the 100HZ EQ slider :annoyed: .
MasterBlaster84
Boomus Fidelis
When I witnessed the issue on thafuzz's box it almost seemed as if the amp ran out of juice which caused it to pop and nearly shutdown until the volume was lowered.
MasterBlaster84 said:
Hmmm, that description is a lot more telling of the condition.
This could be a couple of things. Like MB says, it's possible that the amps were overdriven to the point of being overloaded until it shuts down. If that is the case, then either it's a design issue (impedance of speakers driving amp to overload condition) Solutions to consider (if this is the problem) could be to use 8ohm speakers instead of 4 (or 3, whatever) or attenuating the signal to the amps input. This would result in less volume at the speakers but allow the amp to better handle the situation.
Or perhaps it's possible that the amps are on the fritz (overloading due to thermal overload). If the latter, a more efficient heatsink may help or if the amp is on the fritz, perhaps changing the amp.
Also, it's possible that there is a poor connection someplace. Reflowing the solder connections may help, especially if there are cold solder joints present.
There is a relationship between heat and resistance -- resistance generates heat (think light bulb filiment). If a connection is poor or marginal, it would have resistance. The thing about resistance is that it generates heat which further increases resistance. At some point, resistance would cause so much heat that the connection is broke. So, if there is excessive resistance someplace, then current would seemingly flow fine until it reaches a certain threshold that cuts the power. At that point, heat subsides, current begins flowing again, and sound is restored until it repeats over and over again.
First and foremost on list of things to check is to ensure that all contacts are in good shape and all switches etc. deoxidized.
Just some thoughts.
Gluecifer
Member (SA)
Massive congratulations to you brother Blu Fuzz! Mine does the popping thing too occassionally. I'm almost certain (in my uneducated opinion) that it's the amp's crapping out due to the design being less than properly . Remember, this was a very cheaply put together unit, and I'm still astounded any of them work at all, especially 20 years later on.
These things make Lasonic's look like JVC's by comparison. This is, however, much of their charm.
But great new Blu Fuzz! You can run something line in and enjoy it at a reasonable volume, which is really great compared to the state she was in when you got her.
Rock On.
These things make Lasonic's look like JVC's by comparison. This is, however, much of their charm.
But great new Blu Fuzz! You can run something line in and enjoy it at a reasonable volume, which is really great compared to the state she was in when you got her.
Rock On.
I never thought my BBX would boom again but it is a great feeling.
I am a little confused as to what you guys are calling amps. Do you also refer to these as ICs?
Both ICs were changed out with new ones and that big resistor that was burned up was also replaced.
The pop and speaker movement will occur even if the box was just plugged in and it hasn't had a chance to heat up any parts. All solder connections look as good as new as well.
The option to change out the speakers to an 8ohm would probably calm down the speaker pop & movement. Another good point of changing the speaker to 8ohm is that if anyone else would touch my volume knob and crank it up it would keep the speakers/amps/ICs a little bit safer, correct?
I am listening at about 1/4 volume to avoid having the speaker overload the circuit and blow the ICs.
One thing that still confuses me is the power button...... it still has no on/off capabilities just full on all the time..... :annoyed:
I am a little confused as to what you guys are calling amps. Do you also refer to these as ICs?
Both ICs were changed out with new ones and that big resistor that was burned up was also replaced.
The pop and speaker movement will occur even if the box was just plugged in and it hasn't had a chance to heat up any parts. All solder connections look as good as new as well.
The option to change out the speakers to an 8ohm would probably calm down the speaker pop & movement. Another good point of changing the speaker to 8ohm is that if anyone else would touch my volume knob and crank it up it would keep the speakers/amps/ICs a little bit safer, correct?
I am listening at about 1/4 volume to avoid having the speaker overload the circuit and blow the ICs.
One thing that still confuses me is the power button...... it still has no on/off capabilities just full on all the time..... :annoyed:
blu_fuz said:
An amp is any circuit specifically designed to "amplify" a signal. Amplifier circuits usually consist of a combination of transistors. Boomboxes, especially those built beginning in the late 70's employ the use of amplifiers in the form of IC's. An IC (integrated circuit) is basically a group of semiconductors and their related circuitry, all in one neat package. They simplify the design process. Many have built in thermal shutoff protection and overcurrent protection. If specific parameters are exceeded on an IC employing these protections, the device could automatically shut down or meter the output to protect the IC. There is no way to know if this is what is happening.
However, I find it hard to believe that any manufacturer, even cheap ones, would release a product that could be construed to have bugs or defects off the assembly line. Therefore, I surmise that it was working properly when new and this is a sign of age or wear or component failure. If the design was such that component selection used marginal products to begin with, then it's always on the brink of failure. If I owned your boombox, I would want to re-cap it pronto to eliminate that as a contributing factor. I would also be checking the voltage at load to see if perhaps the power supply is unable to supply the requisite power. I would hope that the new amps were properly heatsinked when they were installed. That means using the appropriate heatsinking compound between the amp tabs and the heatsink. The amp should also be fastened to the heatsink BEFORE soldering the pins. The reason is that the if the device was soldered first, it's almost impossible to get the IC to have good contact with the heat sink.
The power switch? Check the switch with an ohmmeter to see if it's toggling on/off like it's supposed to. That is the first place to start. Second place to check is the cassette switch. Someplace in the mechanical assembly is going to be a microswitch that turns the amp on. This gives the amp power when the cassette mechanism is operated. That's the reason why you don't have to power on the machine to get the tape deck to work -- it has power all the time and can feed power to the amp, bypassing the power switch if it's in the "on" position.
I anticipate posts from you and really look forward to reading them. I know what you are asking me to do but do not know how to read a meter(or where to connect it) nor do I have the time/ability to re-cap the circuits. It would take me weeks to figure out what I needed to replace what is in the box than another few months to have the time to do it.
I'm happy and frustrated at the same time because I wish I had your tools/parts/knowledge to just dive into it. I'm afraid if I try I will damage it.
All I can do is relay what I was told and what I see:
-The ICs/amps were fastened to the heatsink then attached to the board for soldering. The compound put between the heatsink and the IC was put in.
-When I balance to one side(left or right) I can turn the box up about double the volume as I could with both speakers on at the same time.
-Visually, the power switch mechanism is working properly, electronically I don't know.
-The hum from the power supply is fixed. I took it out, peeled the case off and applied high temp black RTV between the supply and the metal case.
-I removed the EQ slider board just to check for damage to the cap side of the board and everything "looks" ok.
-I also spent another 1.5 hours looking everything over for damage, working all switches, knobs, and sliders to see if the situation changed and I didn't find anything.
I'm happy and frustrated at the same time because I wish I had your tools/parts/knowledge to just dive into it. I'm afraid if I try I will damage it.
All I can do is relay what I was told and what I see:
-The ICs/amps were fastened to the heatsink then attached to the board for soldering. The compound put between the heatsink and the IC was put in.
-When I balance to one side(left or right) I can turn the box up about double the volume as I could with both speakers on at the same time.
-Visually, the power switch mechanism is working properly, electronically I don't know.
-The hum from the power supply is fixed. I took it out, peeled the case off and applied high temp black RTV between the supply and the metal case.
-I removed the EQ slider board just to check for damage to the cap side of the board and everything "looks" ok.
-I also spent another 1.5 hours looking everything over for damage, working all switches, knobs, and sliders to see if the situation changed and I didn't find anything.
I have a laptop power supply but it is 18v not 15v like the back of the BBX asks for. Should I try it?
I havn't powered up the box with batteries yet but the AC supply should be the best power it can get right? I guess the power supply could be weak with age and not giving enough juice. I dunno :'-(
I havn't powered up the box with batteries yet but the AC supply should be the best power it can get right? I guess the power supply could be weak with age and not giving enough juice. I dunno :'-(
Blufuz, check the component datasheet for the sanyo LA4508 amp, especially "description of external components" for capacitor C1 which functions also used for the time constant of the pop noise suppressor. Too small capacity makes the pop noise level higher and the recommended value is 100uf to 330uf. You may want to check that. Also, the
http://www.datasheetcatalog.org/datasheet/sanyo/LA4508.pdf
You may want to download and save the datasheet for future reference. I'm pretty sure that a service manual is not available for your boombox so this might be good reference.
Print out and read the datasheet. It contains a lot of useful information regarding circuit design, etc. I also read what seems to suggest that the IC really needs a stable power supply. Again, there is no manual to review, Therefore, I know nothing about the design but from looking at the circuit board, it is so ridiculously simple I really don't think a lot of effort was expended in the design of this boombox. Not to be critical and put down this master blaster but it's really cheaply made and designed.
http://www.datasheetcatalog.org/datasheet/sanyo/LA4508.pdf
You may want to download and save the datasheet for future reference. I'm pretty sure that a service manual is not available for your boombox so this might be good reference.
Print out and read the datasheet. It contains a lot of useful information regarding circuit design, etc. I also read what seems to suggest that the IC really needs a stable power supply. Again, there is no manual to review, Therefore, I know nothing about the design but from looking at the circuit board, it is so ridiculously simple I really don't think a lot of effort was expended in the design of this boombox. Not to be critical and put down this master blaster but it's really cheaply made and designed.
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