Just got done building a pair of Zigmahornets. Now trying to get an amp to drive them.
I bought an assembled TA2020 board from ebay. It's the same board as in this:
http://www.hllyelectronics.com/html/fm_transmitter_1_97.html
The problems are:
1. One of the capacitors (the green one on the top right of the first picture of the board) had a broken leg. What's left is probably too short to be re-soldered onto the board. For a complete newbie like me, I'd appreciate some spoon feeding on what to replace it with. I'm guessing it's a "polyester film" type. It says "104K", then under that "1HD(N)" (N is in a circle). The schematic the seller has on his site shows 104 at this spot. I gathered this is a 100,000pF. I looked on partsexpress.com, but the caps there also have a voltage rating. Not only that, but there are also electrolytic ones. So the questions are 1a) what can I replace this cap with (i.e., what voltage), and 1b) should I stick with polyester film, or would electrolytic be better?
2. While we're on the subject of the capcitor, can anyone suggest possible upgrade to what's on the board? The big cap is an Elna 2200uF. Would this be a good one, or are there better choices?
3. For input, the board has a "standard 2.54mm pcb board connector" (the white part in the bottom right corner of the 3rd picture). Where can I find a plug that can fit? Also, there are three pins, IN1, IN2, and GND. I suppose I'd connect the R+ and L+ to the IN1 and IN2, and R- and L- both to GND? If not, what's the right connection?
TIA for your help!!
Andy
I bought an assembled TA2020 board from ebay. It's the same board as in this:
http://www.hllyelectronics.com/html/fm_transmitter_1_97.html
The problems are:
1. One of the capacitors (the green one on the top right of the first picture of the board) had a broken leg. What's left is probably too short to be re-soldered onto the board. For a complete newbie like me, I'd appreciate some spoon feeding on what to replace it with. I'm guessing it's a "polyester film" type. It says "104K", then under that "1HD(N)" (N is in a circle). The schematic the seller has on his site shows 104 at this spot. I gathered this is a 100,000pF. I looked on partsexpress.com, but the caps there also have a voltage rating. Not only that, but there are also electrolytic ones. So the questions are 1a) what can I replace this cap with (i.e., what voltage), and 1b) should I stick with polyester film, or would electrolytic be better?
2. While we're on the subject of the capcitor, can anyone suggest possible upgrade to what's on the board? The big cap is an Elna 2200uF. Would this be a good one, or are there better choices?
3. For input, the board has a "standard 2.54mm pcb board connector" (the white part in the bottom right corner of the 3rd picture). Where can I find a plug that can fit? Also, there are three pins, IN1, IN2, and GND. I suppose I'd connect the R+ and L+ to the IN1 and IN2, and R- and L- both to GND? If not, what's the right connection?
TIA for your help!!
Andy
Hi Fishline,
Looks like a pretty good board, actually.
Yes, I think a film cap, and I would replace it with the same type, not an electrolytic. 100,000 pf should be 0.1 uf (somebody check my math). Voltage rating here is unimportant, as the films cap voltagfs are all way above what's needed for functionality.
Second, 2200 uf is probably all you need for this board. You might check the specific Elna series number to see if there might be a higher grade of cap (low ESR/low impedance) to replace it, but I'm guessing any change is going to be marginal. Input caps (the big squarish ones) are probably the ones that affect the sound most directly. Search these forums, as there have been a few capacitor shootouts and much lively debate. Looks like the board has multiple holes to caps of different sizes could be fitted.
As for the input, you've got it right. One thing you might do is desolder the pin connector and replace it with a small screw terminal. Radio Shack sells twosies that snap together. You could use two and just leave the fourth unconnected with its pin trimmed off. Or, if you're placing an order with Mouser or Digi-Key, get a three-terminal one. Spacings vary; be sure to check.
As long as you're adding screw terminals, you could do the same for speakers and power. Makes it a lot easier if you're constantly tinkering, as circuit board solder pads tend to come loose after repeated reheating.
Have at it!
--Buckapound
Looks like a pretty good board, actually.
Yes, I think a film cap, and I would replace it with the same type, not an electrolytic. 100,000 pf should be 0.1 uf (somebody check my math). Voltage rating here is unimportant, as the films cap voltagfs are all way above what's needed for functionality.
Second, 2200 uf is probably all you need for this board. You might check the specific Elna series number to see if there might be a higher grade of cap (low ESR/low impedance) to replace it, but I'm guessing any change is going to be marginal. Input caps (the big squarish ones) are probably the ones that affect the sound most directly. Search these forums, as there have been a few capacitor shootouts and much lively debate. Looks like the board has multiple holes to caps of different sizes could be fitted.
As for the input, you've got it right. One thing you might do is desolder the pin connector and replace it with a small screw terminal. Radio Shack sells twosies that snap together. You could use two and just leave the fourth unconnected with its pin trimmed off. Or, if you're placing an order with Mouser or Digi-Key, get a three-terminal one. Spacings vary; be sure to check.
As long as you're adding screw terminals, you could do the same for speakers and power. Makes it a lot easier if you're constantly tinkering, as circuit board solder pads tend to come loose after repeated reheating.
Have at it!
--Buckapound
You folks are extremely helpful! I'll get the 100v 0.1uF film caps.
Can you please show links to the screw terminals at either Rat Shack site or any other? (I'm going to get the caps from partsexpress.com, so if they have it, that'd be great.) I tried searching on rat shack and partsexpress, and got either no hits. mouser's search is rather over my head.
Also, what gauge wires should I use to connect things?
Can you please show links to the screw terminals at either Rat Shack site or any other? (I'm going to get the caps from partsexpress.com, so if they have it, that'd be great.) I tried searching on rat shack and partsexpress, and got either no hits. mouser's search is rather over my head.
Also, what gauge wires should I use to connect things?
Here's an example at Farnell:
http://nl.farnell.com/imo/20-101m-2/terminal-block-pcb-2way/dp/9632670
But also here you have to be very sure about the pitch (distance between the pins) And indeed what wire gauge you want to use them with...
Most of the wiring can doesn't have to be very thick I'd say 0.2AWG will do, but the wires between the amp and power supply can best be pretty thick like 0.8AWG. (I hope I did my math right, I'm not so into American wire gauges....)
An externally hosted image should be here but it was not working when we last tested it.
http://nl.farnell.com/imo/20-101m-2/terminal-block-pcb-2way/dp/9632670
But also here you have to be very sure about the pitch (distance between the pins) And indeed what wire gauge you want to use them with...
Most of the wiring can doesn't have to be very thick I'd say 0.2AWG will do, but the wires between the amp and power supply can best be pretty thick like 0.8AWG. (I hope I did my math right, I'm not so into American wire gauges....)
American wire gauge is some holdover relic of ancient days. The higher the number, the lower the size.
Short runs of speaker and power wire are fine at 18 gauge or so for a small amp like this. Signal wires are often something like 26 gauge.
I can't find the terminals on the Radio Shack site, but if you go to a store, they're hanging on the pegboard right near the printed circuit boards and things like that. Just like V-Bro showed, only peacock blue.
--Buckapound
Short runs of speaker and power wire are fine at 18 gauge or so for a small amp like this. Signal wires are often something like 26 gauge.
I can't find the terminals on the Radio Shack site, but if you go to a store, they're hanging on the pegboard right near the printed circuit boards and things like that. Just like V-Bro showed, only peacock blue.
--Buckapound
Thanks! I had to go to two Radio Shack stores to find the terminals. They only have one pitch size and it didn't fit any of the parts on the amp board. Oh well. I ended up just solder wires longer than I need onto the board. Will trim them once I finalize the arrangement.
Got the amp going last night. Quite nice!
One more spoon-feeding question: The two caps next to the input look like they have adjustment screws on top. What are they for, and do I need to check them? If so, how? (They are marked "64W 50K-K".) Actually I don't know if they are capacitors. The markings on the board say "Rx1" and "Rx2".
Got the amp going last night. Quite nice!
One more spoon-feeding question: The two caps next to the input look like they have adjustment screws on top. What are they for, and do I need to check them? If so, how? (They are marked "64W 50K-K".) Actually I don't know if they are capacitors. The markings on the board say "Rx1" and "Rx2".
Yes, it's basically that simple. 
You see DC voltage makes speaker voice coils act like heaters and when you apply enough it might even melt it. Then your speakers will be dead...
To prevent any of such damage it'd better be as close to zero as possible. It is best done with the inputs of the amp shorted and a little load (speakers are fine) on the output. You can best have another look after the amp is well warmed up and adjust it again.
You see DC voltage makes speaker voice coils act like heaters and when you apply enough it might even melt it. Then your speakers will be dead...To prevent any of such damage it'd better be as close to zero as possible. It is best done with the inputs of the amp shorted and a little load (speakers are fine) on the output. You can best have another look after the amp is well warmed up and adjust it again.
Finally borrowed a DMM from my neighbor. For V DC, it has "2000mV" and "200mV" and no lower. I plugged in the amp and measured one of the channel, turned the screw until it got to ~0.1 on the "200mV" setting on the DMM. I guess that should be alright.
However, when I tried the other channel, I get -619 at the "2000mV" setting on the DMM, and no matter how I turn the screw, it basically didn't change.
Any idea what could be wrong? Suggestion for next step would be much appreciated!
[BTW, if anyone has recommendation for a DMM, that would help a lot, too!]
However, when I tried the other channel, I get -619 at the "2000mV" setting on the DMM, and no matter how I turn the screw, it basically didn't change.
Any idea what could be wrong? Suggestion for next step would be much appreciated!
[BTW, if anyone has recommendation for a DMM, that would help a lot, too!]
Hi v-bro,
Thanks for the reply, but I'm not sure what I'm looking at. If it helps, here's the link to the 4-page user manual in pdf:
http://www.hllyelectronics.com/download.php?action=download&filename=T-AMP-20W.pdf
The schematic is on page 3. On page 2 the table says the DC offset is 5mV typical and 10mV max. I wonder if that's what the setting should be as shipped, or what it should be adjusted to...
Thanks for the reply, but I'm not sure what I'm looking at. If it helps, here's the link to the 4-page user manual in pdf:
http://www.hllyelectronics.com/download.php?action=download&filename=T-AMP-20W.pdf
The schematic is on page 3. On page 2 the table says the DC offset is 5mV typical and 10mV max. I wonder if that's what the setting should be as shipped, or what it should be adjusted to...
Unfortunately the PDF files on the download page are corrupted and unreadable. However you can read the DOC files. Choose and download here:
http://www.hllyelectronics.com/download.php
http://www.hllyelectronics.com/download.php
Hi, well the user manual isn't helping much because there's no schematic or board layout drawings. I wouldn't really know where to start on remote troubleshooting this amp, but I'll do what I can...
The trimmers basically feed the inputs to the chip with compensating DC voltage derived from a resistor (potmeter) that is between 5V and ground. If there is also a broken wire on these components it could explain why it cannot be adjusted....
The potmeter has one pin on ground (measure this!) one pin on 5V (also measure this) and the other pin goes through a large resistor to the input pin on the chip (also try to measure this)... You can download a datasheet of the chip everywhere to look up the pin-out...
http://www.kafka.elektroda.eu/pdf/tripath/TA2020.pdf
Try not to short circuit the chip pins with the probes of the DMM, best is to solder a small piece of wire on the desired pin(s) or closest point and then put voltage on the board.
The output clamping diodes are also suspect, although I doubt if they are broken you'd get an un-adjustable 619mV, mostly this gives massive DC on the output....
The trimmers basically feed the inputs to the chip with compensating DC voltage derived from a resistor (potmeter) that is between 5V and ground. If there is also a broken wire on these components it could explain why it cannot be adjusted....
The potmeter has one pin on ground (measure this!) one pin on 5V (also measure this) and the other pin goes through a large resistor to the input pin on the chip (also try to measure this)... You can download a datasheet of the chip everywhere to look up the pin-out...
http://www.kafka.elektroda.eu/pdf/tripath/TA2020.pdf
Try not to short circuit the chip pins with the probes of the DMM, best is to solder a small piece of wire on the desired pin(s) or closest point and then put voltage on the board.
The output clamping diodes are also suspect, although I doubt if they are broken you'd get an un-adjustable 619mV, mostly this gives massive DC on the output....
Thanks for the pointers, v-bro! I don't know why, Acrobat seems to have problem with that PDF file, but Foxit Reader (my preference over Acrobat) opens it just fine. The schematic and the board layout diagrams are on page 3 and page 4 of the manual (same as in the .doc file). Couldn't you see them?
I'll go get a DMM myself today and check. If you can see the schematics and have more detail suggestions, that'd be great!
I'll go get a DMM myself today and check. If you can see the schematics and have more detail suggestions, that'd be great!
I don't see them on the schematic, either, but then I don't really know how to read a schematic...
v-bro: If you don't mind, could you be extremely explicit in what you mean by "measure this"; i.e., exactly where do I put the test leads and what should I look for? I looked at the TA2020 datasheet, but don't understand what info I'm supposed to glean from it. If you don't mind more spoon-feeding, I'd be very grateful!
v-bro: If you don't mind, could you be extremely explicit in what you mean by "measure this"; i.e., exactly where do I put the test leads and what should I look for? I looked at the TA2020 datasheet, but don't understand what info I'm supposed to glean from it. If you don't mind more spoon-feeding, I'd be very grateful!
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