Onkyo Integra T-4087 and Filter Mods

[Paul C]

Some of you may remember reading over this:

Onkyo T-4017 and Filter Mods

http://audiokarma.org/forums/showthread.php?t=122937

So, here is a similar "Show & Tell" for the T-4087. Like the T-4017 (c.1982), the T-4087 (c.1986) has four filters, two for Wide Mode, two more added for Narrow Mode. The T-4017 had the two Wide filters (X101, X102) first in the chain, and the two Narrow filters (X103, X104) added to the end of the filter chain.

Unlike the T-4017, the T-4087 (and the T-4500) has the Wide filters first and last (X101, X104), with the two Narrow filters (X102, X103) switched in between the Wide filters.

Now, on with the show!

Later in this thread you will see that I have touched up the nicks in the black anodized front, on the top edge, with Birchwood Casey Aluminum Black. A gun shop item.

Yes, that is an output level control. Cool!

That's a European PAL connector. Radio Shack has the correct F to PAL adapter. The way this connector is made into the unit it is too much trouble to change it to an F socket, so I just left it and will use the adapter.

The black plastic part just to the right of the AM terminals is a bracket to hold a plastic loop, which is long gone. I use my own loop antennas anyway.

http://audiokarma.org/forums/showthread.php?t=125817

 

[Paul C]

While I have the tuner open I might as well solder all those wire wrap connections. Done!

The bottom of the circuit board is easily accessable by removing the bottom panel. No need to remove the circuit board and worry about all the jumpers.

This shows the area, outlined in orange, where you will find the filters.

Now a closeup of the filter locations. X101 is a 230 khz GDT type filter. These are very lossy filters. X104 is a 250 khz GDT filter, too. These are the two wide mode filters. X102 and X103, the narrow mode filters are tan-brown, and are 150 khz filters. They are not GDT type, but these older filters have more loss than modern filters, so we will replace them anyway.

Here are the required sockets. They are gold plated "High Reliability" sockets. They can also be bought for a few pennies less just tinned, but gold plated inside the socket where it counts. I just bought these. You can break off however many contacts you need. They come in strips of 10. Also needed is desoldering braid. I find this works better than the vacuum pumps.

You will also need a "pin vise", which holds tiny wire gauge drill bits. After removing the original filters I drilled out the holes just a little bit by hand. This is the safest way to not damage the board. With a Dremel tool accidents happen too easily here. Now the sockets will slip into the holes easily. You can skip the sockets and just solder the new filters directly into the circuit board as they were before, but the use of sockets allows you to experiment with filter types.

 

[Paul C]

This shows the original filters placed back in the sockets in the same position from which they were removed.

Inside my metal workshop, a virtual "Faraday Cage", and just a short piece of wire as an antenna, I have two (out of five) lights on the signal strength meter.

Now I have replaced the first filter, X101 (visible on the far right, now a tan filter instead of blue as in the previous photo), with a new Murata Low Loss 180 khz wide filter. I get these from Greg Gortman at

http://www.dxfm.com/IF filters/IF Filters.htm

Note that there are now three lights on the signal strength. As before, the tuner is switched to Narrow Mode, so all four filters are in the circuit.

Here I have replaced the Narrow Mode filters, X102, X103, with Murata Low Loss 150 khz filters, also from Greg. While these are the same 150 khz bandwidth as the original filters, they have less loss. I have also replaced the last filter, the other Wide Mode filter, X104, with another 180 khz filter. Now there are four (out of five) lights on the signal meter. In addition, the Onkyo APR (Automatic Precision Reception) automatically switched from High Blend On to High Blend Off, as the signal has less noise and the sound quality is now even better.

Not bad for about $12 in parts (filters and sockets) and a few minutes work.


I did have one other little problem... the fake wood sides were in very poor condition.

I will get some shorter screws and just leave the fake sides off for now. I have some speaker projects in the works now, lots of birch ply. I'll use scraps from those projects to make new sides, with the edges taped with birch tape, sand, stain, finish with hand rubbed tung oil. That should do it.

Meanwhile, I'll cut some little inserts and glue in here at the uncovered front corners. I have some 1/8" thick black ABS plastic sheet that will do nicely. I'll glue in with my favorite, E6000.

Done!

 

[ultralc]

Excellent post, as usual. I am wondering if you have compared low loss vs. GDT type.

 

[RxDx]

Someone suggested using toothpicks right behind a hot iron to open PC holes. Avoids using force on the boards.

 

[Paul C]

Ultralc - yes. Murata 230 khz GDT's had noticably more loss than the Murata low loss 180 khz filters. The 230 GDT's had only a little less loss than the original filters. The low loss 180's noticably better. And I could hear no difference in sound quality. Perhaps it could be measured, but if I can't hear it, so what? The ability to pull in stations cleanly that I otherwise could not receive, or would be too noisy to enjoy is what I was looking for.

But if you live in an area with lots of strong stations nearby, you could use GDT's. Putting in the sockets lets you experiment easily.

RxDx, the braid pulled the solder off the holes and left them clear. The reason I had to ream the holes slightly was not because of solder left, but because the pins on the sockets are square (for wire wrap), and I had a little difficulty inserting the square peg in the round hole. Another type of socket might have slipped in easily. But whatever you do, you are right, you don't want to force anything.

Another tip... to solder the sockets in squarely, solder one pin only. Hold a little finger pressure on the opposite side, pushing the socket all the way down, while you reheat that first solder joint. Let it cool. Now you can solder the other two pins.

 

[ultralc]

Thanks Paul. I have read quite a bit about GDT type, but have never experienced it myself.

 

[Paul C]

Two things that are indicative of good selectivity:

(1) I can tune in the weak distant stations on both sides of a strong local without hearing any crosstalk from the strong station.

(2) I can tune in another strong local station where there are no adjacent stations, and there is simply nothing on the adjacent channels, no signal at all. With wider filters I would get a little of the strong station spilling over, but none with the low loss 180's.

 

[audiofreaker]

ha now the pictures are good (must have been a psoting limit ) what did it bring from the original system and to your opinion should any t-4087 owner with cable radio switch to the new system filters and if so why and what would the cost be??

 

[Paul C]

If you are dissatisfied with your T-4087, interference from strong stations, or HD, going to the narrow filters can help. You could skip the sockets, and just install the filters directly into the board. From the source listed in Post #3 in this thread, filters are $1.50 each, plus $2.00 shipping.

4 filters x $1.50 = $6.00
shipping = 2.00

Total $8.00

 

[240sx4u]

Paul, cool...

I have a dumb question, if they are so far superior, why did they not install these types from the factory??

Thanks - Evan

 

[Paul C]

The wider filters gave marginally better distortion figures. But also, we didn't have as much crap crammed into sidebands as we do now. Also, while Murata and others made narrower filters back then, they didn't have the low loss filters like they make now.

Back then those 230 and 280 khz filters were typically 12-14 db insertion loss, as compared to today's 3.5-4.5 db loss for the 180's I used.

And probably they couldn't make the filters as consistently on frequency then, so they had to use wider filters.

And there are more stations on the air now than 20 years ago.

 

[240sx4u]

Cool, thanks!

 

[warnerwhf]

Thank you for the help with the filter mods. It helped my newbie self a lot.

If someone could point out the MPX input and output caps plus the buffer amp out caps I'd sure appreciate it. Even just telling me the area where the caps are that will affect the audio quality will help as I plan on changing all the caps eventually. TIA

 

[bubbajack80]

Cool, thanks!

Did you end up doing these mods to the T-4087?

 

[240sx4u]

I never had a T-4087 it was more a curiosity I guess, hard to say for sure since that was 20 years ago.