RCI 2990 low volume in all modes

[Lkaskel]

Hi Gang,
II am working on two 2990's with the same issue. The volume is only about 25% of the expected loudness when turned all the way up. I did a receive alignment on it and it is receiving very well. These are pre-2000's radios and have the EPT295013Z boards in them. I replaced the 2 electrolytic caps (213 and 217) in the audio path and that had no effect. There is not much after to audio chip. Any thoughts?
Also, on the 1st radio there was a diode and resistor soldered to the bottom of the board near the voltage regulator but they were not done in a factory way. At least I don't think so. Do you?

 

[nomadradio]

C224 and C46? Bridging a good cap across the foil pads of one, then the other would tell you if either cap in the radio has gone open.

Quickest way I know to tell.

73

 

[loosecannon]

the diode and resistor are just the usual NPC mod found on this chassis.
LC

 

[nomadradio]

It would be surprising to see the exact same fault in two radios, but I would also check pin 9 of the TA7222P speaker-amp chip. Should be close to one-half the DC voltage seen at pin 1, the chip's power-input pin.

Pin 9 is the next-to-rearmost pin. Pin 1 is at the end towards the front of the radio.

73

 

[loosecannon]

how can you tell they are receiving well?
will they hear down past -110 dbm?

it might be time to look at some of the weird things that can happen over time.

how is the connection being made by RL1?
use a continuity meter to check that there is no resistance there being caused by corroded or old and worn out contacts.

could the speaker jacks themselves be getting worn out?

having two radios with the exact same problem points to either an external source for the problem, or possibly something that will fail in all radios made at that time at that factory.
LC

 

[Lkaskel]

It would be surprising to see the exact same fault in two radios, but I would also check pin 9 of the TA7222P speaker-amp chip. Should be close to one-half the DC voltage seen at pin 1, the chip's power-input pin.

Pin 9 is the next-to-rearmost pin. Pin 1 is at the end towards the front of the radio.

73

Hi Nomad,

Pin 1 - 13.8vdc
Pin 9 - 13.2vdc

Regarding the same fault in 2 radios, that relay of info is somewhat on me. The user has 2 2990's pre 1999 and "said" that they both exhibit the same problem. I have only checked one at this point and at startup it had very low volume. I did a quick receive alignment and it does receive well. 12db sinad at -120db. I replaced C46 and C224 and it still has low volume.

 

[Lkaskel]

how can you tell they are receiving well?
will they hear down past -110 dbm?

it might be time to look at some of the weird things that can happen over time.

how is the connection being made by RL1?
use a continuity meter to check that there is no resistance there being caused by corroded or old and worn out contacts.

could the speaker jacks themselves be getting worn out?

having two radios with the exact same problem points to either an external source for the problem, or possibly something that will fail in all radios made at that time at that factory.
LC

Hey Loose Cannon,

I did a quick receive alignment and it does receive well. 12db sinad at -120db. I have not tested the second radio as the 1st one did exhibit the issue stated by the user. I did think about the relay and would have expected that it would vary a little if the contacts were worn but maybe not. Its a sealed relay as well.

 

[nomadradio]

Pin 1 - 13.8vdc
Pin 9 - 13.2vdc

(sound of raucous klaxon horn)

Pin 9 needs to be half the reading at pin 1. Acceptable range would have been between 6 and 7 Volts DC. They read nearly the same. This indicates likely damage to the TA7222P audio chip. Any time this part is changed, we also change the output-blocking capacitor C213. Any time it goes bad, it can damage that chip.

And the speaker.

Cheap insurance.

The only other faults I know that can cause the voltage reading you saw on pin 9 would be a short in either C217 or C219. Easy enough to find out. Unsoldering one lead of either cap so that it won't touch the edge of the foil pad will take it out of the circuit.

If doing this changes the DC voltage reading at pin 9, this cap has a problem. And if taking one lead out of the circuit (for either cap) does NOT change this reading, that capacitor is NOT the root of the problem, and the TA7222P chip has the problem.

Don't know how many counterfeits of that part are out there, but UTSource on Ebay is fairly reliable. Haven't gotten a fake chip from them yet.

73

 

[Lkaskel]

(sound of raucous klaxon horn)

Pin 9 needs to be half the reading at pin 1. Acceptable range would have been between 6 and 7 Volts DC. They read nearly the same. This indicates likely damage to the TA7222P audio chip. Any time this part is changed, we also change the output-blocking capacitor C213. Any time it goes bad, it can damage that chip.

And the speaker.

Cheap insurance.

The only other faults I know that can cause the voltage reading you saw on pin 9 would be a short in either C217 or C219. Easy enough to find out. Unsoldering one lead of either cap so that it won't touch the edge of the foil pad will take it out of the circuit.

If doing this changes the DC voltage reading at pin 9, this cap has a problem. And if taking one lead out of the circuit (for either cap) does NOT change this reading, that capacitor is NOT the root of the problem, and the TA7222P chip has the problem.

Don't know how many counterfeits of that part are out there, but UTSource on Ebay is fairly reliable. Haven't gotten a fake chip from them yet.

73

Ok....so Covid head is a real thing!!! The truth is, I did get Covid many months back and have still not recovered. It has been amazing to see how much it can affect the mind.

Anyway......
I went back and looked at the radio again this morning and what I did not notice the 1st time was that the audio chip has 10 pins and 1 pin is not used. With that, I checked it again this time on pin 9 (not 10) and did have 6.57vdc so I am assuming at this point that the audio chip is ok. The owner does not want to invest in a full recap at this point. It is the strangest thing. When I listen on 38lsb I get clear stations and expected signal strength on the s-meter but the volume remains low even on an external speaker. By "low" I mean at max volume it is at the same loudness as other radios at 2-3 (out of 10).

Sorry for the miss on the pin 9 measurement!!

 

[Handy Andy]

This has me wondering if it's not the output of the Audio amp - what about the input side?

Thinking the Bootstrap or the input AF Amp that takes the Volume control output and that has a cap C224 a simple 1uF 50V cap. You're thinking age so lets look at this from a standpoint of - If I was this radio and I was built when Ronald Regan was still in office - He's' gone - I'm not - so why do I still hear echoes?

I'm referring to the typical "Thunk" heard from a power on this thing does.

I mean a side to side comparison is probably out of the question but if "low volume" - is there something further up causing this?

It mean spend some quality time with it - put it by the fireplace and offer some marshmallows - talk to it nicely and then threaten to use a very hot poker to resolder some of those cold solder joints it's been creaking and groaning about as of late...

(The above is Done In Jest - do not attempt to do this type of repair at home or with a hot poker)​

I'm referring to the quality of audio not quantity - there may be a failed cap - but like at C46 the AF Mixer deconversion (Q16) or questionable Q17 SQ amp - kinda acting like it wants to but - nah - too old to start acting like I'm a kid again - sort of operation - marginal cap (read highly resistive ESR rating) Thats C49 the output line from the IC1 Quad Op amp - so a recap may not be in order but this sounds like it wants to be...

The Things got a PA - so use that same speaker and try it on the PA MODE to see if you GET A REALLY REALLY LOUD SQUEAL from it...if you do - then recheck the Volume control and its' support parts - like that cap.

You can then rule out the Audio Amp - the problem is further upstream

 

[Lkaskel]

This has me wondering if it's not the output of the Audio amp - what about the input side?

Thinking the Bootstrap or the input AF Amp that takes the Volume control output and that has a cap C224 a simple 1uF 50V cap. You're thinking age so lets look at this from a standpoint of - If I was this radio and I was built when Ronald Regan was still in office - He's' gone - I'm not - so why do I still hear echoes?

I'm referring to the typical "Thunk" heard from a power on this thing does.

I mean a side to side comparison is probably out of the question but if "low volume" - is there something further up causing this?

It mean spend some quality time with it - put it by the fireplace and offer some marshmallows - talk to it nicely and then threaten to use a very hot poker to resolder some of those cold solder joints it's been creaking and groaning about as of late...

(The above is Done In Jest - do not attempt to do this type of repair at home or with a hot poker)​

I'm referring to the quality of audio not quantity - there may be a failed cap - but like at C46 the AF Mixer deconversion (Q16) or questionable Q17 SQ amp - kinda acting like it wants to but - nah - too old to start acting like I'm a kid again - sort of operation - marginal cap (read highly resistive ESR rating) Thats C49 the output line from the IC1 Quad Op amp - so a recap may not be in order but this sounds like it wants to be...

The Things got a PA - so use that same speaker and try it on the PA MODE to see if you GET A REALLY REALLY LOUD SQUEAL from it...if you do - then recheck the Volume control and its' support parts - like that cap.

You can then rule out the Audio Amp - the problem is further upstream

Hi Andy,
So, I fired up the wood stove and sat with a beverage and the radio for a while. I then took the hot poker and.....well, never mind......

While I was at it I did check the only cap you mentioned (C49) that had not been replaced yet and replaced it. One interesting note here, that cap was mounted to the bottom of the board instead of through the top. The solder job was decent so maybe they did that at the factory...

The cap replacement did not help and when I hooked up a speaker to the PA it was not very loud. The mic gain was all the way up and the speaker was sitting next to the radio. Do you agree that this is sounding more and more like the audio chip?

Thanks as always!

 

[Handy Andy]

Shoot - thanks for trying...

Well, if it is the audio chip - the thing running that low - would be VERY HOT from excessive input and drive out.

I mean - if it was working as an audio amp - because the amp certainly seems to be working - but unless there is some form of failure - you should be able to take an ordinary speaker - and place it right across the output cap to ground - or from this point even a DVM set for continuity look at the speaker built in and try to locate the "ZERO" dead short to it. If the line to the speaker is correct, you'd see only 8Ω on one side to speaker terminals and the other side would be "0" and a BEEP if so equipped.

I've had to do this to find the corrected polarity of the speaker - but then too - I've also seen speaker wiring that has had bad wiring - in this case age.

So if the SQ amp was ok - and PA seems low too - then YES the output seems odd to be as low as it is...

Did you check @loosecannon post on seeing if the relay to the speaker was ok?

This continuity check might help show if the relays contacts are bad.

 

[Lkaskel]

Well, It's working. I couldn't take it. i decided to do a partial recap. I essentially did the right hand side of the board. About 15 caps. I powered it up and wow, it works. I actually think it was C219 as Nomad suggested.

Men, I will say this. I had my butt kicked by Covid a few months back and it really has messed my head up. My mind is like I'm always operating on 24hrs with no sleep. Doing something as simple as a recap was interesting. I have it very organized. A magnetic tray for screws, an old plastic butter tub for the old caps, solder on the left, desolder machine and iron on the right..... It took me quite a while to get myself sorted to even get into the flow but it sure was nice even if it was only 15 caps!!

I can't tell you all how much I appreciate each of you for your patience and thoughtfulness in your responses!!! I've got about 10 years until retirement and I am hoping that this "hobby" is something I can use to fill some of my time and knowing that this community exists gives me hope.

 

[Handy Andy]

Only 10 years?

It will go fast...

In my past 10 years got remarried, Buried Dad, Took Care of Mom, buried her too, Raised two pups and they're buried - now I'm just waiting for either me or the wife...

So - no, not here to sound morbid, burying everything we've got, but that in the lifetime of this short span of a decade - a LOT has happened during this time. And all of it was, in what seems, a blink of an eye.

In reflection, it makes you appreciate that having a good attitude and passion for making friends - whether by wireless or in person - thru wireless - makes life far more enjoyable.

Thanks for putting up with us...