I'm pretty sure both DMMs have a diode function built in, as well as continuity.  The chinese one has more features and auto-ranging but I use the craftsman if I care about the readings being as accurate as possible, haha.

Put it in diode mode and put the leads across all combinations of the transistor junctions. So E-C, C-E, C-B  etc. if it is blown, one or more will show no voltage drop ie. 0 voltage in diode mode and if the meter has audio it will beep

The meter will apply a small voltage and show the voltage drop if the junction is good. Range balls will be 0.3 to 0.8 somewhere in there

I won't be home until after 5PM CST today, but I'll take a look at that.

What I gave you is for PNP transistors. I don't remember what you get for NPN, it might be different, but still doable.

I fixed my bought used AL-80B doing that and found 2 bad transistors and a diode and fixed it.

Current meters are short circuits.  That can make using them dangerous.
Voltage meters appear as really high loads.

I agree on checking all the diodes, easy to do.

FYI - Did call Yaesu to see if they had an answer, they no longer offers component-level advice or troubleshooting over the phone due to "liabilities."  Once it gets to that point, where I'm at right now, they can only recommend that I send it in to them for repair.

So I'll keep aiming to perform those diode tests after work unless we can think of anything else that might need testing.

Mach - Snuck out of work a bit early and now at my desk at home.  What exactly am I testing here?  Not sure which transistors or if I'm doing this test right.  Radio on or off?

Here is a link to a high-res photo of the PA board, and embedded below is a smaller version - https://i.imgur.com/nP1x2BH.jpg

Attached File


I'm probably doing something wrong, but I've tested 3 transistors on that board so far and I'm getting reverse results from what I should be getting....meaning I'm measuring an NPN transistor(according to the part number) but getting results that should be for a PNP, and vice versa.  It's probably me.

Those 3 big white things with 3 soldered ends on each side are the power transistors.

I think the one without white past is the exciter that drives the HF finals and the VHF/UHF finals.

The one in the middle is probably the HF final and the one on the bottom is probably the VHF/UHF finals.

I think they are all NPN.

One of the middle tangs in the collector, the opposite middle tang is the base and the 4 on the ends are the emitter, I think.

so start on the transistor without the white past, in diode test mode, ( radio unpowered ) put the probes on the 2 middle tangs and see what the meter says, then reverse them and see what it says.

do that for all 3 transistors and see what the diffeence is in readings. I think they should show a voltage drop from 0.3-.8, most likely around 0.7

then do one of the middle to any of the 4 ends, then reverse the leads, then the other middle to any of the 4 ends anf reverse the leads.

do that with all 3 transistors and write down the readings notting which reading is for red lead on which one and black lead on which one.

if one or more of these values show zero, then that is a bad transistor junction

try to post what you get. you dont have to unsolder anything, do this with them on the board. A bad transistor junction should show zero voltage drop with the diode tester. If you get one that has zero voltage drop both ways, then that is a bad junction.

I thought I had saved the blown transistors I took out of my amp but I can't find them to verify.

I think if the junction ( which is basicly a diode ) is good  say between the emitter and the base, one way with the probes will yeild a reading of one and when you reverse the probes the other way should be a 0.7 voltage drop. If it is blown it should show zero in both directions meaning it is a short circuit.

So to recap, you will get zero voltage drop between any of the 4 end tangs because those are really all connected to the emitter.

so probe readings on a the 2 middle tangs, one middle and one of the 4 ends, and then the other middle tang and one of the 4 ends. Reversing the probes for each set of tangs measured.

It doesn't matter which is the base, emitter, or collector since you are testing all combinations. All combinations should yield a 1 or a 0.7 on the meter.

Blown reads 0 and 0 again when the probes are reversed.

This will work for NPN.

The only difference between PNP and NPN is what readings you get with red on one and black on the other, but by doing it both ways with the probes, it won't matter. One way will be a 1 reading and the other way will be a 0.7 reading. Blown is still zero

I ran diode tests on those three PA transisters.  Here are the results starting at the top PA transistor and working down(top two are same part no);

Left Middle(+) and Top(-) reads 0.003v
Left Middle(+) and Bottom(-) reads 0.003v
Right Middle(+) and Top(-) reads 0.051v
Right Middle(+) and Bottom(-) reads 0.051v

Left Middle(+) and Top(-) reads 0.003v
Left Middle(+) and Bottom(-) reads 0.003v
Right Middle(+) and Top(-) reads 0.051v
Right Middle(+) and Bottom(-) reads 0.051v

Left Middle(+) and Top(-) reads 0.025v
Left Middle(+) and Bottom(-) reads 0.025v
Right Middle(+) and Top(-) reads 0.051v
Right Middle(+) and Bottom(-) reads 0.051v

Each test the voltage reading would start out at some random higher number and drop/settle at the values above.

Same values with polarity reversed.

Also, it's the bottom PA transistor that's getting hot I think.  Not the area of the board above it.  Tested this by jumping those pins to complete that circuit and let that current hit the PA transistors.

I thought it was the area of the board above it because I was paying more attention to the laser designation of my IR temp gun and not where the actual sensor was pointing.  Perhaps that PA transistor is blown or shorted and that's causing such a massive current draw?

That's what I think also. Only a few components in there will take a constant 6.5 amps and not smoke. Finals will take it.

You could unsolder the final and lift the tab to take it out of circuit to verify.

Looking at the photo of the circuit board... see all that flux around the three power transistors leads?

Look at all the other components on the board.  See any flux?  No, because it is all cleaned off as part
of the production process.

Someone changed the transistors, left the flux, did not clean it off (which is not necessary), and apparently
there are other problems causing them to overheat.  In all likelihood, this radio had problems before it came
to you.

Jup

That does not make any sense to me unless you are getting current flow through resistors in the circuit from the diode test function.

Looking at the diagram from top to bottom with the transformer on the right, the transistors are Q3018, Q3017, and Q3016. Q3018 and Q3017 should be the same part 2SC2782. The Parts list show them as 2SC5125 but that part is obsolete and replaced with 2SC2782. Q3016 the one on the bottom is indeed the UHF Final Power Transistor.

Looking at the diagram, TP3021 is 13.8V. TP3022 goes to the collector through an inductor to Q3016 and it should be 300ma from TP3022. If you go up the other way from TP3022 it should be 300ma and that goes to a transformer. I am just guessing, but if that transformer was taking 6.5 amps it would probably smoke and open up and there would be zero current. So my assumption is that the 6.5 amps is not going to the transformer which is the HF route. So it must be going through Q3016 which is the UHF route.

You already confirmed that the current when the HF variable resistor is changed, that 6.5 amps goes up some meaning the HF section seems to be working.

I would suggest you try adjusting the pot for the UHF section and see if you get an increase or decrease in the current between those 2 TP points. That might confirm the UHF section is not working.

Another option would be to unsolder Q3016 and test it out of the board, but then I think you risk being able to give it back to the seller and surface mount components are delicate to solder and unsolder.

I agree with a poster above that said based on the flux, all 3 transistors have been changed in the past.

Another thing to try is to try transmitting on UHF and see what the power output is. My guess is that it is very low or nothing.

You could try buying a new 2SC3102  ( Q3016) but doing a quick search it looks like it is only available from china directly on ebay, RFparts does not carry it.  I read on a forum that Yaesu changed the FT-897 PA board.

At this point if it was me, I would either send it to Yaesu to fix it or give it back for a refund.

It looks like the Q3106 is likely blown, you can't tell with it on the board because of the surrounding components, and many times if a transistor is blown there are other parts that are blown too either causing the transistor to be blown or because the transistor is blown.

Here is one more thing you can test.

Q3015 biases Q3016. VR01 is the adjustment pot for tthe UHF idling current set for 300ma.

Test Q3015. It is the bottom left of you pic. It is labelled D1801

Test all three combinations like you did the others.

There are 3 leads. The short one is the collector.
The long one closest to the short one is the emitter.
The long one on the other side of the short one furthest away is the  base.

test them the same see if you get any zero voltage drops.

If that has blown, it looks like it would drive Q3016 UHF final into saturation and draw max current.

I'll test Q3015 and try adjusting VR01 when I get to the house.

As for pulling Q3016 to test or replace, if this was one of the other two finals I'd be all for buying a hot air rework station to do it myself and learn something but the VHF/UHF final is a bit more complicated.  It has tiny caps/resistors(need to check layout to see what they are) between its fingers and I'm not sure I could do this without messing something up.  Plus like you had mentioned I run the risk of another underlying issue/bad component that caused the final to blow, or something else gone bad due to the final blowing.  Looking more like I'll need to send this out for repair but it'll go to the Radiosmith, not Yaesu.  I took a look at some of their reviews and they're not so great.

The way I see it...the tuner and power supply alone are $450+ for the pair(current lowest retail prices), and I'm only in to the whole setup for $550.  Even if I have to drop $200 to get the radio repaired and aligned/adjusted, $750 for the whole setup still isn't too bad.

I think I just confirmed a blown VHF/UHF Q3016 final.

Moved the dummy load over to the VHF/UHF side, tuned in to the 2m band, changed the on-screen meter from SWR to PWR, when keying mic it reads up to the fourth bar and does not fluctuate as I talk.

Moved the dummy load back over to the HF side, tuned in to the 20m band, no PWR reading just keying but if I talk it fluctuates up.

Don't have a real wattmeter to confirm the numbers, but that should be sufficient enough evidence of a blown final?

If you are on FM in 2m and UHF, then you won't see varying power output like on SSB.

It will be a constant power reading as the amplitude of the signal doesn't change when modulated, only the frequency is varied.

Removing those finals isn't that big of a task. I used to use one of those de-soldering irons

with the suction bulb built onto it. Remove as much solder with the de-soldering iron

then heat and peel the tabs off the board. Remove mounting screw(s) and remove device. Then clean the solder

pads up and get rid of old heatsink compound and flux. Install new device with new compound and tighten mounting screws.

Solder tabs down. Done. I've done quite a few that way, probably hundreds of them actually in my "career".

I did find that no matter if I ran RF Power at 5 or 20, the power meter read the same keying on 2m or 70cm, still stuck in the same place.  I would assume that increasing or decreasing the watts would cause the PWR reading to increase or decrease, wouldn't it?

This particular PA transister has numerous little caps soldered between fingers making it a bit trickier of a job.  I'm just going to send it off to Steve to have him diagnose/repair and also take care of getting it aligned/biased so it's 100% for me.

Also have an MFJ-815D SWR/wattmeter and MFJ 260c dry dummy load on the way.

Sorry I have not read every response but I have read most. Has anyone mentioned removing the jumper that supplies 13.8v to the collector of the driver and finals? If they are shorted, or have low resistance to ground or the base, when you remove the Vcc (+13.8v) from the collector you should see the current draw fall off to near 0 and there should be very little heat produced. The jumper should be between TP3021 and TP3022. I can send you the service manual if needed.

Attached File

Hi SVGA, yeah, he did that.

Okay cool.

Your keydown on 2m and hf sounds normal to me. Except the power should have changed on 2m when you adjusted the power setting and it did not which is consistant with a constant 6.5 amps going through the power transistor

The final for UHF may not be blown. The transistor may just be biased on all the time and 6.5 amps all the time is making it hot.

I think the key is testing Q3015. If that is bad then that is driving Q3016 to on.

I still dont understand how Q3016 could be blown when you get the same numbers from the other power transistors.

All those voltages you measued are too small. No matter what is connected to the transistor in the circuit  you can't change the semiconductor voltage drop ( .7 or so ) if it is good and if it is bad it will be a short.

Are you sure you had the meter in diode test setting? What meter are you using?is the battery in the meter good.

Plus you never measured left middle to right middle

I already have it all buttoned back up and packaged to send out to the repair guy.  Figured it was probably best that a pro work on this, plus I can have him do all the bias adjustments and tuning since it's likely not been done in a few years.

My buddy, the seller, made me take a $250 refund on it because he felt terrible for selling a radio he thought worked 100%.  I kept insisting he didn't have to buy the radio back or give me anything else since it probably just needs a final and he would have never known about the issues because A. he never had to touch the case, and B. he only used it for HF, but he insisted on covering the repair so I'll take that and use it on whatever the repair bill is.

I will definitely update the thread once I hear from Steve on what was wrong with it.

Cool news is my dummy load and swr/wattmeter will be here tomorrow.  Bad news is I don't have a radio to use them on for a few weeks.

That seller sounds like a solid dude.  Keep him around

I concur

Honest guy

He's definitely a good dude, old school, and has been playing mentor for me whenever I have questions about the hobby.  He's not too big in to radio diagnostics/repair, typically just sends his radios off for that stuff.  He really did feel terrible about the whole thing as if it was his fault.   I've been eyeing his shack every time I'm over at his place to see if there is anything I can get him as a thank you gift.  Thinking a new MFJ dummy load to upgrade from his leaky old MFJ paintcan or something like that.

I always thought one of those clocks that shows UTC and local time would be a good ham gift.

edit: for HF guys, anyway

The radio is in transit and will be delivered to the repair guy on Wednesday.  Will keep you guys posted once he finds the issue.

Standing by for fix info.

I'm proud of the OP.
He sure learned a lot more than a simple 'plug and play'!

Radio is delivered and next in line for diagnosis after he ties up the Ten-Tec Titan III he has pulled apart on the bench.

This definitely was a fun and valuable learning experience for me.  I learned quite a bit about my radio and how to do various component tests, how to adjust and measure the different bias settings, etc.

Do not neglect to report back, what the tech found was wrong with your radio, which parts were
replaced, and how it performs when you get it back.

Definitely won't forget.

Still nothing new to report yet.  Last I heard from him was Wednesday night when he said I was next in line after the Ten-Tec amp, haven't followed up with him yet since he's probably busy being one of the top repair guys on eham.

When it comes back I'll be limited to dummy load tests until I get licensed, but if it's all good then I should be able to see proper PWR readings on the screen when transmitting on VHF or UHF.  Before it appeared to be locked in at only a few watts regardless of me adjusting RF power which was another sign the final was blown.  I don't know how off receiving was, if at all, but once he lets me know what it needs I will have him do all the bias adjustments/tuning to get it all back in to spec.

Bad news so far.

I'm currently trying to decide how much I'd want to spend on this radio to fix it.  Right now I'm $300 in to the radio+tuner+power supply and $100 in to shipping and evaluation/first hour to Steve.  The tuner and power supply alone are worth $400+ so I'm not in a bad spot yet, but that can quickly change if this repair bill ends up doubling that amount or more.  On the one hand, I don't want to go down the rabbit hole on this and spend a fortune.  On the other hand, it's a good setup and even at a total investment of $800 I'd still be hard pressed to find the same exact kit in functioning order for that amount. Technically, at $400 so far I've paid just under retail for the tuner and power supply and got a free radio...but maybe I'm just seeing it that way because I want this thing fixed so badly, haha.

At this point I think he's waiting on me to approve another $45 hour evaluation fee since he's not done digging through it.  I'm probably ok spending 200, 300, maybe even 400 to get this thing repaired but that's probably where I'd draw the line and either keep it as an HF-only rig or get that refund on it from my buddy.  My aim is still to get it fixed at this point, so I'll keep you guy posted on his analysis and the final quote.

That Stinks.
Did your friend ever use it on VHF-UHF?
Just wondering if he had an antenna or feed line problem that perhaps caused this problem.

This was an HF-only rig for him and sat up on a shelf on his shack desk so he never had any idea this thing was overheating and not working on VHF/UHF.  I don't know how long he owned it and if the person before him messed it up.  That VHF/UHF final was definitely worked on at some point and poorly soldered, and my buddy doesn't do repairs so it wasn't him.  If he can't simply unplug a part and swap it, he sends it off for repair.

At this point it sounds like the only parts it needs are the VHF/UHF final and the tiny caps that were soldered between the legs of the final, and I'm estimating around $50-60 for those parts.  The final alone is around 30-35 bucks and getting harder to find unfortunately.

I don't know enough about this stuff to make sense of his diagnosis on the 80m power issue possibly being caused by the low-pass filter.  Not sure if that's something that can be adjusted, or another part that needs to be replaced.

I e-mailed Steve back to see what his estimate is right now on it or if he was needing another hour eval on it to finish diagnosis and prepare a more accurate estimate/quote.  Waiting for his reply.

If I were in that spot I would do another hour at least.

Then ask for a shipped repaired cost and decide if I can justify that or just get it back.  But then I would probably try to fix it myself once the problems are all identified.

Steve replied again, doesn't sound promising.  Seems like he thinks it might be a jump down an expensive rabbit hole on this repair, meaning he could replace the final and caps but then once he's able to finally test VHF/UHF there could be other problems.  He's also pointed out several times that this thing has likely been cooking that area of the PA board for a while, if the heat was enough to make those caps fall apart there could be other damage he hasn't found yet.  Here's what he sent me...

On the one hand, I've come to really like this radio and know how to operate it well by now so I'd love to have it fixed.  I may also just be attached to this radio because I got in to the whole kit(radio+auto tuner+power supply) for so cheap, and to get another setup like that based off something current like the ft-857d would likely run upwards of $1500.  It's a lot easier to get approval from the SO to spend $300 than $1500.

On the other hand this could easily start off at $150 worth of parts/labor(bare minimum to replace the final, could be more) and end up leading to more parts/labor to get any other VHF/UHF issues fixed, then whatever the parts/labor cost is to fix the power issue on 80m which he hasn't been able to diagnose yet since he already ran out the clock on my initial 1-hour analysis.

If I back out now I'm out the cost of the $45 analysis, $50ish shipping to him, whatever shipping costs to get it back, and I get a $300 refund from my buddy and I hand the whole setup back to him.  Ultimately I'd be sitting around a $150 loss from this experience and back to just having my HT to play with, plus two antennas(HF and dual band) that would be un-used until I got another base radio to set up at the house.

If I stick to it, there's no telling what the total cost would be or any guarantee that he could completely fix the radio since there are still some unknowns.

Decisions, decisions.

Johnny,
You could have him disconnect the current drawing components and then keep it as a receiver and/ or wait and buy a working pull PA board and have it realigned then. hth
73,
Rob

If I remove the bridge across those two pins mentioned earlier in the thread I'm pretty sure that opens the VHF/UHF circuit and stops the overheating but it still receives fine in all bands and would only transmit on HF bands.  So I could probably use it for receive and HF, use the HT for dual-band, and be out $450 at that point, and hopefully find a clean PA board in the future to get it back to 100%.  Or I return it for my $300 and walk away $150 in the hole on it.  I'll do some thinking on that.

I just e-mailed Steve to let him know I'm going with his gut on this one and opting out of the repairs.   This experience was definitely a low-blow.  I know I'm not going to find a full kit like that again for anywhere near what I paid for this one.  Probably should have held off on buying the dummy load, swr/wattmeter, coax, connectors, and antennas.

If he told me "I checked the transmitter on HF and 6m. With the exception of 80m, where it is only making 60% - 70% of the power it should, it appears to be working properly. "

I would have him leave the VHF/UHF final disconnected and run it as-is.  It's still usable on HF even with the low output on 80m.

He's probably also right about a problem in the bandpass filter for 80m.

<---Nailed it on a shorted final.

I just read the whole thing. This kind of sucks. It's your radio and your money but I would not spend too much on repairs. Based on the picture on page 1, it's a 4 out of 10 condition, at best. 6.5 Amps idle current probably "cooked" a lot of components nearby. Excess heat often causes delamination on the circuit boards which may lead to more problems in the future.
Is VHF/UHF very important for you? If not, have him fix the HF side and keep it the way it is. It's a great little radio but if you really get into working HF bands, you will most likely get a better base HF station and keep this radio as a portable rig. Just guessing, of course. Keep in mind that a brand new FT-891 sells for a little over $600 and it has a better receiver and some cool modern features. A new IC-7300 will probably sell for around $1000 next month, during the Dayton hamvention.

You've probably made the right choice by bailing out on the repairs.  If I were you, I'd look for a used FT-891 to get on HF.  I managed to get a lightly used one back in September of 2017 for $450.  Match with a MFJ-939Y and you're in business with a good combination for home or portable work.  I know, it won't do VHF/UHF, but you'll probably find either little use for VHF/UHF after a while or realize it's easier and cheaper to just have a dedicated rig for VHF/UHF.

I can vouch for the FT-891 and MFJ-949Y setup. I use that portable and in my truck and it is a great combination and less than $800 for the combination new

I was thinking about a used FT-891 for HF, and a used FT-8800r for dual-band because it has the dual-listen which I think I'd like.  I want to cover all bands and moving forward I think it's best I do this with multiple radios rather than a shack-in-a-box radio.  I wouldn't mind having a fully functional ft-897d for mobile use, but I'm sure I'll come across another all band transceiver later on down the road that I can toss in the truck.